Chloroprene latex composition

Abstract

One embodiment of the present invention relates to a chloroprene latex composition and a method for producing an adhesive product, wherein the chloroprene latex composition contains a chloroprene latex (A) containing a chloroprene-based polymer satisfying requirement (a-1), and a tackifier (B) having a softening point of 85-155°C as measured by a ring-and-ball method. (a-1) The tetrahydrofuran insoluble fraction α [mass%] in 100 mass% of the chloroprene-based polymer and the melting enthalpy β [mJ / mg] of the chloroprene-based polymer as measured by differential scanning calorimetry (DSC) satisfy the following formula. Logβ ≥ −0.022 × α + 1.0

Description

Chloroprene latex composition

[0001] One embodiment of the present invention relates to a chloroprene latex composition.

[0002] Chloroprene latex is a latex containing a chloroprene polymer. Chloroprene polymer is a polychloroprene obtained by emulsion polymerization of 2-chloro-1,3-butadiene (hereinafter also referred to as "chloroprene"), and exhibits high cohesive strength and crystallinity. Chloroprene polymers are mainly produced by emulsion polymerization, and chloroprene polymer latex (chloroprene latex), in which polymer particles after polymerization are dispersed in water, can be applied to substrates without dissolving the chloroprene polymer in a solvent and is known as an environmentally friendly water-based adhesive (Non-Patent Document 1). Water-based adhesives based on chloroprene latex are used, for example, in furniture, shoes, civil engineering and construction, wetsuits, and the like.

[0003] In recent years, in response to the tightening of global regulations on organic volatile substances, there has been a shift from solvent-based adhesives to water-based adhesives that have a smaller environmental impact, leading to an increasing demand for water-based adhesives containing chloroprene latex, and various water-based adhesives have been proposed. For example, Patent Document 1 discloses a water-based adhesive that contains zinc oxide and polychloroprene latex obtained by emulsion polymerization in the presence of acetoacetylated polyvinyl alcohol.

[0004] Here, chloroprene-based adhesives are often used as contact adhesives, and water-based adhesives using chloroprene latex are also used as contact adhesives. In adhesion using a contact adhesive, the contact adhesive is applied to the adhesion surfaces of the adherends, dried to form adhesive layers, and the adhesive layers are then bonded together, thereby developing adhesive strength.

[0005] JP 2012-176999 A

[0006] "Improvement of Chloroprene Adhesives", Kanenari Goda, Journal of the Society of Rubber Industry of Japan, Vol. 52, No. 3, March 1979, pp. 167-178

[0007] As described in Non-Patent Document 1, when a water-based adhesive containing chloroprene latex is used as a contact adhesive, the formation of an adhesive layer takes time because the water, which is the dispersion medium of chloroprene latex, takes time to dry. As a result, there is a problem that bonding takes longer than with solvent-based adhesives. Furthermore, if the adhesive layer is bonded in a state where it has not dried sufficiently and water remains in the adhesive layer, the initial adhesive strength is insufficient and the adhesive layers are prone to peeling. Furthermore, there is room for improvement in the normal adhesive strength after curing the bonded product obtained by bonding the adhesive surfaces, and there is also the problem that peeling is prone to occur in high-temperature (60°C or higher) environments.

[0008] When the adhesive composition described in Patent Document 1 was used as a contact adhesive, if the water, which was the dispersion medium of the latex, was not dried sufficiently, the initial adhesive strength, normal adhesive strength, and heat resistance were insufficient. That is, with the adhesive composition described in Patent Document 1, if the adhesive composition was not dried until the adhesive layer was completely dry, the initial adhesive strength, normal adhesive strength, and heat resistance were insufficient, and the adhesive composition did not function sufficiently as a contact adhesive.

[0009] One embodiment of the present invention provides a chloroprene latex composition that is excellent in initial adhesive strength, normal adhesive strength, and heat resistance compared to conventional water-based contact adhesives, even when used as a contact adhesive in a state where a dispersion medium remains in an adhesive layer (i.e., a layer containing the solid content of the chloroprene latex composition).

[0010] As a result of further research, the present inventors have found that the above-mentioned problems can be solved by the following configuration example. The configuration example of the present invention is as follows. In this specification, "A to B" indicating a numerical range means A or more and B or less.

[0011] [1] A chloroprene latex composition (X) comprising: a chloroprene latex (A) containing a chloroprene polymer satisfying the following requirement (a-1); and a tackifier (B) having a softening point of 85 to 155°C as measured by the ring and ball method (based on the measurement method of JIS K 5902). (a-1) The tetrahydrofuran-insoluble content α [mass%] of 100 mass% of the chloroprene polymer and the melting enthalpy β [mJ / mg] of the chloroprene polymer as measured by differential scanning calorimetry (DSC) satisfy the following formula (1): Logβ≧−0.022×α+1.0 (1)

[0012] [2] The chloroprene latex composition (X) according to [1], wherein the chloroprene latex (A) comprises: a first chloroprene latex containing a chloroprene polymer having a tetrahydrofuran insoluble content of 0 to 15% by mass and a melting enthalpy of 10 to 40 [mJ / mg]; and a second chloroprene latex containing a chloroprene polymer having a tetrahydrofuran insoluble content of 70 to 98% by mass and a melting enthalpy of 0 to 10 [mJ / mg].

[0013] [3] The chloroprene latex composition (X) according to [2], wherein, based on 100% by mass of a solid content contained in the chloroprene latex (A), a content of the solid content derived from the first chloroprene latex is 1 to 99% by mass, and a content of the solid content derived from the second chloroprene latex is 99 to 1% by mass.

[0014] [4] The chloroprene latex composition (X) according to any one of [1] to [3], wherein the chloroprene latex (A) contains an anionic emulsifier.

[0015] [5] The chloroprene latex composition (X) according to [4], wherein the anionic emulsifier is a rosinate salt.

[0016] [6] The chloroprene latex composition (X) according to any one of [1] to [5], wherein the tetrahydrofuran-insoluble content α [mass%] and the fusion enthalpy β [mJ / mg] further satisfy the following formula (2): Log β≦−0.006×α+1.7 (2)

[0017] [7] The chloroprene latex composition (X) according to any one of [1] to [6], wherein the tackifier (B) contains a compound containing a carboxyl group.

[0018] [8] The chloroprene latex composition (X) according to [7], wherein the tackifier (B) contains a reaction product of an unsaturated carboxylic acid or an acid anhydride with a rosin.

[0019] [9] The chloroprene latex composition (X) according to [8], wherein the unsaturated carboxylic acid or acid anhydride is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, and cinnamic acid.

[0020]

[10] The chloroprene latex composition (X) according to any one of [1] to [9], containing 3 to 90 parts by mass of the tackifier (B) per 100 parts by mass of a solid content of the chloroprene latex (A).

[0021]

[11] The chloroprene latex composition (X) according to any one of [1] to

[10] , wherein the amount of solid content of the chloroprene latex composition (X) is 40 to 70 mass%, when the mass of the chloroprene latex composition (X) is 100 mass%.

[0022]

[12] The chloroprene latex composition (X) according to any one of [1] to

[11] , further containing a pH adjuster (C).

[0023]

[13] The chloroprene latex composition (X) according to

[12] , wherein the pH adjuster (C) is at least one selected from the group consisting of amino acids, organic acids, and inorganic weak acids.

[0024]

[14] The chloroprene latex composition (X) according to

[12] or

[13] , wherein the pH adjuster (C) is a weak acid having at least one logarithm of the reciprocal of its acid dissociation constant (pKa) at 25°C in the range of 8.0 to 11.0.

[0025]

[15] The chloroprene latex composition (X) according to any one of

[12] to

[14] , wherein the product of the amount [mmol] of the pH adjuster (C) used per 100 g of a solid content of the chloroprene latex (A) and the valence of the pH adjuster (C) is 0.1 to 30 mmol.

[0026]

[16] A method for producing an adhesive product, comprising: a step (1) of adhering the chloroprene latex composition (X) according to any one of [1] to

[15] to at least a part of each of a first adherend and a second adherend; a step (2) of drying the chloroprene latex composition (X) adhered to the first adherend and the chloroprene latex composition (X) adhered to the second adherend to form a layer containing a solid content of the chloroprene latex composition (X); and a step (3) of adhering the layer formed on the first adherend and the layer formed on the second adherend by bringing them into contact with each other.

[0027] According to one embodiment of the present invention, a chloroprene latex composition can be provided that is excellent in initial adhesive strength, normal adhesive strength, and heat resistance compared to conventional water-based contact adhesives, even when used as a contact adhesive in a state where a dispersion medium remains in the adhesive layer (i.e., a layer containing the solid content of the chloroprene latex composition).

[0028] 1 is a graph showing the relationship between the Log β value calculated from the melting enthalpy β (mJ / mg) of a chloroprene polymer in a chloroprene latex and the tetrahydrofuran-insoluble content of the chloroprene polymer, and a straight line on the graph represented by formula (1).

[0029] <Chloroprene Latex Composition (X)> The chloroprene latex composition (X) includes a chloroprene latex (A) containing a chloroprene polymer satisfying predetermined requirements, and a tackifier (B) having a softening point of 85 to 155°C measured by a ring and ball method (in accordance with the measurement method of JIS K 5902).

[0030] <Chloroprene Latex (A)> The chloroprene latex (A) is a latex in which a chloroprene polymer satisfying the requirement (a-1) described below is dispersed in a dispersion medium such as water. Examples of the dispersion medium include water and aqueous solvents containing water and a water-soluble alcohol, and water is preferred.

[0031] [Chloroprene Polymer] The chloroprene polymer contained in the chloroprene latex (A) satisfies the following requirement (a-1).

[0032] [Requirement (a-1)] When the tetrahydrofuran-insoluble content in 100 mass% of the chloroprene polymer is α [mass%] and the fusion enthalpy of the chloroprene polymer measured by differential scanning calorimetry (DSC) is β [mJ / mg], α and β satisfy the following formula (1), preferably also satisfy the following formula (1a), and more preferably also satisfy the following formula (1b): Log β ≧ −0.022 × α + 1.0 (1) Log β ≧ −0.014 × α + 1.1 (1a) Log β ≧ −0.009 × α + 1.2 (1b) Here, the tetrahydrofuran-insoluble content α [mass%] and the fusion enthalpy β [mJ / mg] are both determined by the method described in the Examples below. The tetrahydrofuran-insoluble content is the content ratio of components insoluble in tetrahydrofuran at 25°C.

[0033] When the chloroprene polymer in the chloroprene latex (A) satisfies formula (1), the chloroprene latex composition (X) containing the chloroprene latex (A) tends to have excellent initial adhesive strength, normal adhesive strength, and heat resistance. Here, the initial adhesive strength refers to the adhesive strength immediately after laminating layers containing a solid content prepared by drying the chloroprene latex composition (X) together, or a short time (e.g., 5 minutes) after laminating them together. The normal adhesive strength refers to the adhesive strength after laminating layers containing a solid content prepared by drying the chloroprene latex composition (X) together and aging them for a long time (e.g., 24 hours). The initial adhesive strength can be, for example, the adhesive strength after 5 minutes has elapsed after laminating layers containing a solid content obtained by applying the chloroprene latex composition (X) to an adherend and drying them for 10 minutes at 23°C and 50% relative humidity. Specifically, the initial adhesive strength can be determined by the method described in the Examples below. The normal adhesive strength can be, for example, the adhesive strength after layers containing solids are bonded together and then aged for 24 hours under conditions of 23°C and 50% relative humidity, and can be determined specifically by the method described in the examples below.

[0034] The layer containing solids prepared by drying the chloroprene latex composition (X) may be a layer containing solids entirely wet with a dispersion medium such as water, a layer containing solids partially wet, or a layer containing solids entirely dried. The layer containing solids may be in a state where a part or the whole of the layer containing solids is swollen with a dispersion medium.

[0035] Although the description in this specification is not intended to be bound by any particular theory, it is presumed that the reason why the chloroprene latex composition (X) has excellent initial adhesive strength and normal adhesive strength when the chloroprene polymer satisfies formula (1) is due to the following (a1) to (a3): (a1) The higher the tetrahydrofuran-insoluble content of the chloroprene polymer, the more likely the initial adhesive strength and normal adhesive strength of the solid layer containing the chloroprene polymer are to increase. (a2) The higher the tetrahydrofuran-insoluble content of the chloroprene polymer, the more likely the crystallinity of the chloroprene polymer is to decrease. (a3) ​​The higher the crystallinity of the chloroprene polymer, the more likely the initial adhesive strength and normal adhesive strength of the solid layer containing the chloroprene polymer are to increase. Note that the higher the crystallinity, the greater the value of the enthalpy of fusion.

[0036] A chloroprene polymer satisfying formula (1) can be obtained by adjusting the tetrahydrofuran-insoluble content and melting enthalpy (i.e., crystallinity) of the chloroprene polymer. The tetrahydrofuran-insoluble content in the chloroprene polymer can be controlled by the polymerization conversion rate, the amount of chain transfer agent used in producing the chloroprene polymer, the polymerization time, the polymerization temperature, and the like. The longer the polymerization time, the higher the polymerization conversion rate tends to be. Furthermore, increasing the polymerization conversion rate tends to increase the tetrahydrofuran-insoluble content in the chloroprene polymer. Furthermore, increasing the amount of chain transfer agent tends to decrease the tetrahydrofuran-insoluble content in the chloroprene polymer.

[0037] The melting enthalpy (i.e., the degree of crystallinity) of a chloroprene polymer can be controlled by the polymerization temperature during polymerization of the chloroprene polymer. The lower the polymerization temperature during polymerization of the chloroprene polymer, the larger the melting enthalpy and the higher the degree of crystallinity. Furthermore, the higher the tetrahydrofuran content of the chloroprene polymer, the smaller the melting enthalpy and the lower the degree of crystallinity.

[0038] When the tetrahydrofuran-insoluble content α [mass %] of the chloroprene polymer and the melting enthalpy β [mJ / mg] of the chloroprene polymer satisfy the above formula (1), the upper limit of the value of Log β is not particularly limited, but usually satisfies the following formula (2), more preferably the following formula (2a), and even more preferably the following formula (2b): Log β≦−0.006×α+1.7 (2) Log β≦−0.007×α+1.6 (2a) Log β≦−0.008×α+1.5 (2b)

[0039] The chloroprene latex (A) may contain chloroprene polymers derived from a plurality of chloroprene latexes. Here, the chloroprene polymers derived from a plurality of chloroprene latexes may differ from each other in one or more physical properties such as monomer composition, particle size, tetrahydrofuran insoluble content, and fusion enthalpy. For example, the chloroprene latex (A) may contain chloroprene polymers having the same monomer composition but different tetrahydrofuran insoluble content and fusion enthalpy. Alternatively, the chloroprene latex (A) may contain chloroprene polymers having approximately the same tetrahydrofuran insoluble content and fusion enthalpy but different particle sizes.

[0040] When chloroprene polymers derived from multiple chloroprene latexes are contained in chloroprene latex (A), it is sufficient that the chloroprene polymers contained in chloroprene latex (A) as a whole satisfy formula (1). For example, multiple chloroprene latexes containing chloroprene polymers not satisfying formula (1) may be combined so that the chloroprene polymers contained in the obtained chloroprene latex (A) as a whole satisfy formula (1). Alternatively, a chloroprene latex containing a chloroprene polymer not satisfying formula (1) may be combined with a chloroprene latex (A) containing a chloroprene polymer satisfying formula (1) so that the chloroprene polymers contained in the obtained chloroprene latex (A) as a whole satisfy formula (1). Furthermore, multiple chloroprene latexes (A) containing chloroprene polymers satisfying formula (1) may be combined so that the chloroprene polymers contained in the obtained chloroprene latex (A) as a whole satisfy formula (1).

[0041] When the chloroprene latex (A) contains a plurality of types of chloroprene polymers, it is preferable that the chloroprene latex (A) contains a first chloroprene polymer having a relatively low tetrahydrofuran-insoluble content and a relatively high fusion enthalpy, and a second chloroprene polymer having a relatively high tetrahydrofuran-insoluble content and a relatively low fusion enthalpy, since the chloroprene polymers as a whole are likely to satisfy formula (1). For example, it is preferable that the chloroprene latex (A) contains the following first chloroprene polymer and second chloroprene polymer: a first chloroprene polymer having a tetrahydrofuran-insoluble content of 0 to 15% by mass and a fusion enthalpy of 10 to 40 mJ / mg; a second chloroprene polymer having a tetrahydrofuran-insoluble content of 70 to 98% by mass and a fusion enthalpy of 0 to 10 mJ / mg.

[0042] The tetrahydrofuran-insoluble fraction of the first chloroprene polymer is preferably 0% by mass or more. The tetrahydrofuran-insoluble fraction of the first chloroprene polymer is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. The upper and lower limits of the tetrahydrofuran-insoluble fraction of the first chloroprene polymer may be any combination. The melting enthalpy of the first chloroprene polymer is preferably 10 mJ / mg or more, more preferably 12 mJ / mg or more, and even more preferably 15 mJ / mg or more. The melting enthalpy of the first chloroprene polymer is preferably 40 mJ / mg or less, more preferably 37 mJ / mg or less, and even more preferably 35 mJ / mg or less. The upper and lower limits of the melting enthalpy of the first chloroprene polymer may be any combination.

[0043] The tetrahydrofuran-insoluble fraction of the second chloroprene polymer is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 78% by mass or more. The tetrahydrofuran-insoluble fraction of the second chloroprene polymer is preferably 98% by mass or less, more preferably 96% by mass or less, and even more preferably 94% by mass or less. The upper and lower limits of the tetrahydrofuran-insoluble fraction of the second chloroprene polymer may be any combination. The melting enthalpy of the second chloroprene polymer is preferably 0 mJ / mg or more, more preferably 0.05 mJ / mg or more, and even more preferably 0.10 mJ / mg or more. The melting enthalpy of the second chloroprene polymer is preferably 10 mJ / mg or less, more preferably 7 mJ / mg or less, and even more preferably 5 mJ / mg or less. The upper and lower limits of the melting enthalpy of the second chloroprene polymer may be any combination.

[0044] The first chloroprene polymer and the second chloroprene polymer may or may not satisfy the formula (1) individually.

[0045] When the first chloroprene polymer and the second chloroprene polymer are used in combination, the mass ratio of the first chloroprene polymer to the second chloroprene polymer in the chloroprene latex (A) (first chloroprene polymer:second chloroprene polymer) is not limited as long as the chloroprene polymers as a whole satisfy the above formula (1), but is preferably 1:99 to 99:1, more preferably 10:90 to 90:10, even more preferably 40:60 to 85:15, and particularly preferably 50:50 to 75:25.

[0046] When the first chloroprene polymer and the second chloroprene polymer coexist, the crystallization rate of the first chloroprene polymer tends to be slower than when the first chloroprene polymer is present alone. Therefore, in chloroprene latex composition (X) in which the first chloroprene polymer and the second chloroprene polymer coexist, the amount of the first chloroprene polymer that crystallizes during drying of the composition to form a solids-containing layer tends to be smaller than when the first chloroprene polymer is present alone. As a result, the contact strength (adhesion) immediately after adhesion tends to be higher and the initial adhesive strength tends to be higher than when the first chloroprene polymer is present alone. For these reasons, it is believed that when the mass ratio of the first chloroprene polymer to the second chloroprene polymer (first chloroprene polymer:second chloroprene polymer) is 50:50 to 75:25, the contact strength and initial adhesive strength are likely to be particularly good. Even when the first chloroprene polymer and the second chloroprene polymer coexist, it is believed that after bonding and aging for a relatively long period of time (e.g., 24 hours at 23°C and 50% relative humidity), crystals of the first chloroprene polymer are formed to the same extent as when the first chloroprene polymer is present alone. The crystallized chloroprene polymer has inferior contact strength compared to before crystallization, but improved adhesive strength. Therefore, when the first chloroprene polymer is present in a larger amount than the second chloroprene polymer, it is presumed that the adhesive strength of the chloroprene polymer as a whole in the chloroprene latex (A) is increased due to the formation of crystals of the first chloroprene polymer.

[0047] The composition and physical properties of the chloroprene polymer that can be contained in the chloroprene latex (A) will be described below.

[0048] A chloroprene-based polymer is a polymer containing 2-chloro-1,3-butadiene (also referred to as "chloroprene") as the main monomer component. Here, "main monomer component" refers to the component that is contained in the largest proportion among the monomers that derive the structural units contained in the polymer. When the total amount of the monomers that derive the structural units contained in the polymer is taken as 100 parts by mass, the "main monomer component" is preferably a monomer component that is contained in an amount of 80 parts by mass or more. A chloroprene-based polymer may be composed only of structural units derived from chloroprene, or may be composed of structural units derived from chloroprene and structural units derived from monomers copolymerizable with chloroprene.

[0049] The monomer copolymerizable with chloroprene is not particularly limited as long as it does not interfere with the object of the present invention, and examples thereof include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid and its esters, and methacrylic acid and its esters. Among these, the monomer copolymerizable with chloroprene is preferably 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, and methacrylic acid, more preferably 2,3-dichloro-1,3-butadiene and methacrylic acid, and particularly preferably 2,3-dichloro-1,3-butadiene. The monomer copolymerizable with chloroprene may be one type alone or two or more types.

[0050] In a chloroprene-based polymer, the amount of structural units derived from chloroprene is preferably 80 parts by mass or more, more preferably 85 parts by mass or more, and even more preferably 88 parts by mass or more, where the sum of chloroprene and monomers copolymerizable with chloroprene is 100 parts by mass. The amount of structural units derived from chloroprene is preferably 100 parts by mass or less. Furthermore, when a chloroprene-based polymer contains structural units derived from 2,3-dichloro-1,3-butadiene, the amount of the structural units may be more than 0 parts by mass, with the upper limit being preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 12 parts by mass (where the total of all structural units constituting the chloroprene-based polymer is 100 parts by mass). The amount of monomers copolymerizable with chloroprene other than 2,3-dichloro-1,3-butadiene is preferably 5 parts by mass or less, where the total of all structural units constituting the chloroprene-based polymer is 100 parts by mass. When the composition of the chloroprene polymer in the chloroprene latex composition (X) is within the above range, the cohesive strength and functionality derived from the copolymerized monomer can be imparted without impairing the flexibility and high cohesive strength inherent to polychloroprene.

[0051] The z-average particle size of the chloroprene polymer particles is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 90 nm or more. The upper limit of the z-average particle size is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 210 nm or less. The z-average particle size is determined by the method described in the Examples below. The upper and lower limits of the z-average particle size of the chloroprene polymer particles may be combined in any combination. Having the z-average particle size of the chloroprene polymer particles within the above range is desirable because it provides high emulsion stability for the latex particles and extends the shelf life of the adhesive composition. The z-average particle size of the chloroprene polymer particles can be adjusted by the type and amount of surfactant used during polymerization. Specifically, using a surfactant with high emulsifying ability tends to reduce the z-average particle size of the resulting chloroprene polymer particles. Furthermore, the greater the amount of surfactant added, the smaller the z-average particle size of the resulting chloroprene polymer particles tends to be.

[0052] The melting enthalpy β [mJ / mg] of the chloroprene polymer measured by differential scanning calorimetry (DSC) is preferably 0 mJ / mg or more, more preferably 3 mJ / mg or more, and even more preferably 5 mJ / mg or more. The melting enthalpy β [mJ / mg] of the chloroprene polymer is preferably 40 mJ / mg or less, more preferably 25 mJ / mg or less, and even more preferably 20 mJ / mg or less. The melting enthalpy is determined by the method described in the Examples below. The method for preparing a chloroprene polymer having a desired melting enthalpy is as described above. The upper and lower limits of the melting enthalpy β [mJ / mg] of the chloroprene polymer may be any combination.

[0053] [Chloroprene latex (A)] The chloroprene latex (A) can be any latex in which a chloroprene polymer satisfying the requirement (a-1) is dispersed in a dispersion medium such as water. The chloroprene latex (A) may contain a plurality of chloroprene latexes.

[0054] When the chloroprene latex (A) contains a plurality of chloroprene latexes, it is sufficient that the chloroprene polymers contained in the chloroprene latex (A) as a whole satisfy the formula (1). That is, the chloroprene latex (A) may be prepared by combining a plurality of chloroprene latexes containing a chloroprene polymer not satisfying the formula (1). Alternatively, the chloroprene latex (A2) may be prepared by combining a chloroprene latex containing a chloroprene polymer not satisfying the formula (1) with a chloroprene latex (A1) containing a chloroprene polymer satisfying the formula (1). Furthermore, the chloroprene latex (A5) may be prepared by combining a chloroprene latex (A3) containing a chloroprene polymer satisfying the formula (1) with a chloroprene latex (A4) containing a chloroprene polymer satisfying the formula (1).

[0055] For example, the chloroprene latex (A) may contain the following first chloroprene latex and second chloroprene latex: A first chloroprene latex containing the first chloroprene polymer having a tetrahydrofuran insoluble content of 0 to 15% by mass and a melting enthalpy of 10 to 40 mJ / mg A second chloroprene latex containing the second chloroprene polymer having a tetrahydrofuran insoluble content of 70 to 98% by mass and a melting enthalpy of 0 to 10 mJ / mg Either the first chloroprene latex or the second chloroprene latex may or may not fall under the chloroprene latex (A) on its own.

[0056] By mixing the first chloroprene latex and the second chloroprene latex, the chloroprene polymer in the resulting chloroprene latex as a whole tends to satisfy the formula (1). As a result, the chloroprene latex (A) is easily obtained, and the layer containing the solid content of the chloroprene latex composition (X) prepared using the chloroprene latex (A) tends to have good initial adhesive strength and normal adhesive strength.

[0057] When the first chloroprene latex and the second chloroprene latex are mixed, the amount of solids derived from the first chloroprene latex, relative to 100% by mass of solids contained in the chloroprene latex (A), is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 40% by mass or more. Furthermore, the amount of solids derived from the first chloroprene latex, relative to 100% by mass of solids contained in the chloroprene latex (A), is preferably 99% by mass or less, more preferably 90% by mass or less, and even more preferably 75% by mass or less. The upper and lower limits of the amount of solids derived from the first chloroprene latex relative to 100% by mass of solids contained in the chloroprene latex (A) may be any combination.

[0058] When the first chloroprene latex and the second chloroprene latex are mixed, the amount of solids derived from the second chloroprene latex, relative to 100% by mass of solids contained in the chloroprene latex (A), is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 25% by mass or more. Furthermore, the amount of solids derived from the second chloroprene latex, relative to 100% by mass of solids contained in the chloroprene latex (A), is preferably 99% by mass or less, more preferably 90% by mass or less, and even more preferably 60% by mass or less. The upper and lower limits of the amount of solids derived from the second chloroprene latex relative to 100% by mass of solids contained in the chloroprene latex (A) may be any combination.

[0059] It is presumed that when the first chloroprene latex and the second chloroprene latex are mixed so that the solid contents of each are in the above-mentioned ratio, in the resulting chloroprene latex (A), the crystallization of the first chloroprene polymer is inhibited by the second chloroprene polymer. As a result, in the chloroprene latex composition (X) containing the chloroprene latex (A), the amount of the first chloroprene polymer that crystallizes during drying of the composition to form a layer containing a solid content is relatively small, and the layer containing the solid content has good contact properties and initial adhesion. Here, although the crystallization rate of the first chloroprene polymer is slow, the crystallization of the first chloroprene polymer progresses over time, and it is presumed that the crystallization of the first chloroprene polymer improves the normal adhesive strength.

[0060] The solids concentration of the chloroprene latex (A) is preferably 40% by mass or more, more preferably 43% by mass or more, and even more preferably 45% by mass or more, based on 100% by mass of the chloroprene latex (A). The solids concentration of the chloroprene latex (A) is preferably 73% by mass or less, more preferably 71% by mass or less, and even more preferably 70% by mass or less, based on 100% by mass of the chloroprene latex (A). The upper and lower limits of the solids concentration of the chloroprene latex (A) may be any combination. When the solids concentration of the chloroprene latex (A) is within the above range, it is easy to adjust the solids concentration of the chloroprene latex composition (X) to a suitable range described below. As a result, a chloroprene latex composition (X) having good initial adhesive strength and normal adhesive strength can be easily prepared. The solid content refers to the components remaining after removing components that volatilize under the solid content measurement conditions, such as solvents and volatile components, from a latex or emulsion. The solid content of the chloroprene latex (A) includes not only the chloroprene polymer but also emulsifiers used during production. Specifically, the solid content concentration (mass%) of the chloroprene latex (A) can be determined by dividing the weight (Wd) of a dried product obtained by drying the chloroprene latex (A) by the mass (Wa) of the sampled chloroprene latex (A) in an oven at 100°C for 2 hours, and multiplying the result by 100 (i.e., Wd / Wa × 100). The solid content concentration (mass%) of the chloroprene latex (A) can be appropriately adjusted depending on the polymerization conversion rate, the amount of emulsifier used, and the like.

[0061] The chloroprene latex (A) may contain, in addition to the chloroprene polymer and the dispersion medium, the emulsifier used in preparing the chloroprene latex (A). Preferably, the chloroprene latex (A) contains an anionic emulsifier. More preferably, the chloroprene latex (A) contains a rosinate salt as the anionic emulsifier. When the chloroprene latex (A) contains an anionic emulsifier, the emulsion state is moderately destabilized during the drying process, making it easier for the chloroprene latex (A) to exhibit tack, which is important for adhesives. Furthermore, when the anionic emulsifier is a rosinate salt, it has good compatibility with the chloroprene polymer and does not inhibit the adhesive performance of the chloroprene polymer.

[0062] [Method for Producing Chloroprene Latex (A)] The method for obtaining the chloroprene latex (A) is not particularly limited, but emulsion polymerization is preferred, and industrially, aqueous emulsion polymerization is particularly preferred. For example, chloroprene alone, or chloroprene and a monomer copolymerizable with chloroprene, may be emulsion polymerized in the presence of an emulsifier, preferably a metal salt of rosin acid, and optionally using a polymerization initiator and a chain transfer agent, and when a predetermined polymerization conversion rate is reached, a polymerization inhibitor may be added to terminate the polymerization.

[0063] The type of emulsifier for the chloroprene latex (A) is not particularly limited, but examples thereof include anionic emulsifiers and nonionic emulsifiers, with anionic emulsifiers being particularly preferred.

[0064] The type of anionic emulsifier is not particularly limited, but examples thereof include alkali metal salts of rosin acid, dodecylbenzenesulfonates (such as sodium dodecylbenzenesulfonate and triethanolamine dodecylbenzenesulfonate), diphenyl ether sulfonates (such as sodium diphenyl ether sulfonate and ammonium diphenyl ether sulfonate), naphthalenesulfonates (such as sodium salts of β-naphthalenesulfonic acid formaldehyde condensates), and alkali metal salts of fatty acids (such as potassium laurate), with alkali metal salts of disproportionated rosin acid being particularly preferred.

[0065] The type of rosin acid is not particularly limited, but examples include gum rosin, wood rosin, tall rosin, disproportionated rosin obtained by disproportionating these, and purified rosin, with disproportionated rosin being preferred. As the metal salt, an alkali metal salt is usually used, preferably a sodium salt and / or a potassium salt. Alternatively, rosin acid and an alkali metal hydroxide may be added separately to form an alkali metal salt of rosin acid.

[0066] The type of nonionic emulsifier is not particularly limited, but examples include polyvinyl alcohol, partially saponified polyvinyl alcohol, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene lauryl ether, etc., with partially saponified polyvinyl alcohol being particularly preferred. These emulsifiers may be used alone or in combination of two or more. It is preferable that the emulsifier contains a metal salt of rosin acid.

[0067] When a metal rosinate salt is included as an emulsifier, its content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of charged monomer. The upper limit of the metal rosinate salt content is 8 parts by mass or less, more preferably 6.5 parts by mass or less, and even more preferably 5.0 parts by mass or less. By setting the metal rosinate salt content within the above range, polymerization stability during emulsion polymerization can be improved, and the appropriate number of micelles formed can suppress heat generation at the initial stage of polymerization and maintain a desired viscosity during polymerization. The above-described metal rosinate salt content is based on the charged monomer, and is therefore slightly lower than the solids content of the polymer. Any combination of the upper and lower limits of the metal rosinate salt content is acceptable.

[0068] The content of the metal rosinate in the chloroprene latex (A) is preferably 0.55 parts by mass or more, more preferably 1.1 parts by mass or more, and even more preferably 1.65 parts by mass or more, relative to 100 parts by mass of the chloroprene polymer in the chloroprene latex (A). The upper limit of the content of the metal rosinate in the chloroprene latex (A) is preferably 8.8 parts by mass or less, more preferably 7.15 parts by mass or less, and even more preferably 5.5 parts by mass or less, relative to 100 parts by mass of the chloroprene polymer in the chloroprene latex (A). The upper and lower limits of the content of the metal rosinate in the chloroprene latex (A) may be any combination.

[0069] As the initiator for the polymerization of chloroprene-based polymers, a conventional radical polymerization initiator can be used. For example, in the case of emulsion polymerization, conventional organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, and ammonium persulfate, and azo compounds such as azobisisobutyronitrile are used. In addition, a co-catalyst such as anthraquinone sulfonate, potassium sulfite, or sodium sulfite can be used as appropriate.

[0070] In the production of the chloroprene latex (A), a molecular weight modifier (chain transfer agent) may be used during polymerization in order to obtain a polymer having a desired molecular weight and distribution. The chain transfer agent is not particularly limited, and examples thereof include alkyl xanthogen disulfides such as dithiobis(thioformate) O,O-diisopropyl, and alkyl mercaptans such as dodecyl mercaptan. The chain transfer agent may be used alone or in combination of two or more.

[0071] In the production of the chloroprene latex (A), in order to obtain a polymer having a desired molecular weight and distribution, a polymerization terminator may be added to terminate the reaction when a predetermined polymerization conversion rate is reached. The polymerization terminator is not particularly limited, and commonly used terminators such as phenothiazine, para-t-butylcatechol, hydroquinone, hydroquinone monomethyl ether, and diethylhydroxylamine can be used.

[0072] <Tackifier (B)> The tackifier (B) is added to improve the adhesiveness of the chloroprene latex composition (X) and the contact properties of the chloroprene polymer. In particular, in the present invention, the addition of a specific tackifier can improve the contact properties in a short-term dry state.

[0073] The amount of tackifier (B) is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the solids content of the chloroprene latex (A). The amount of tackifier (B) is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of the solids content of the chloroprene latex (A). The upper and lower limits of the amount of tackifier (B) may be any combination. By including the tackifier (B) in the above ranges, the adhesiveness of the chloroprene latex composition (X) and the contact adhesiveness of the chloroprene polymer can be improved. This improves the initial adhesive strength, normal adhesive strength, and heat resistance of the chloroprene latex composition (X). As a result, even when a layer containing the solid content of the chloroprene latex composition (X) is used as a contact adhesive in a state containing a dispersion medium, it can exhibit good contact properties as well as good initial adhesive strength, normal adhesive strength, and heat resistance.

[0074] The softening point of the tackifier (B) (measured by the ring and ball method (based on the measurement method of JIS K 5902)) is 85°C or higher, preferably 90°C or higher, and more preferably 95°C or higher. The softening point of the tackifier (B) is 155°C or lower, preferably 150°C or lower, more preferably 147°C or lower, even more preferably 130°C or lower, and particularly preferably 115°C or lower. The upper and lower limits of the softening point may be any combination. When the tackifier (B) has a softening point within the above range, the adhesiveness of the chloroprene latex composition (X) can be maintained at high temperatures, and the heat resistance can be improved. The tackifier (B) may be used alone or in combination of two or more types.

[0075] When the tackifier (B) is used in the form of an emulsion or a solution as described below, the amount of the tackifier (B) is the amount of solids excluding the solvent and the like.

[0076] The type of tackifier (B) is not particularly limited, and examples thereof include rosin resins or rosin ester resins, reaction products of unsaturated carboxylic acids or acid anhydrides with rosin (rosin resins or rosin ester resins), petroleum resins such as terpene phenolic resins, aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, and hydrogenated versions of these, and alkylphenolic resins. The tackifier (B) may contain a compound containing a carboxyl group. When the tackifier (B) contains a compound containing a carboxyl group, the compound containing a carboxyl group is preferably a reaction product of an unsaturated carboxylic acid or acid anhydride with rosin. When the tackifier (B) contains a compound containing a carboxyl group, the initial adhesive strength of the layer containing the solid content produced by drying the chloroprene latex composition (X) tends to be improved. When the tackifier (B) contains a compound containing a carboxyl group, the initial adhesive strength of the adhesive layer tends to be good even when the drying time is so short that the adhesive layer is not sufficiently dried (i.e., when the dispersion medium remains in the adhesive layer containing the solid content of the chloroprene latex composition (X)). Note that when the tackifier (B) contains a compound containing a carboxyl group, the initial adhesive strength tends to be good even when the adhesive layer containing the solid content of the chloroprene latex composition (X) is dry.

[0077] Examples of rosin resins and rosin ester resins include gum rosin, tall rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated products thereof, and esterified products thereof. The reaction product of an unsaturated carboxylic acid or acid anhydride with rosin is a compound obtained by reacting a rosin resin or a rosin ester resin with an unsaturated carboxylic acid or acid anhydride. Examples of unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and cinnamic acid. Examples of acid anhydrides include maleic anhydride and itaconic anhydride. Two or more types of unsaturated carboxylic acids and acid anhydrides may be used. The two or more types of unsaturated carboxylic acids used may be two or more types of unsaturated monocarboxylic acids, two or more types of unsaturated dicarboxylic acids, or a mixture of one or more types of unsaturated monocarboxylic acids and one or more types of unsaturated dicarboxylic acids. Alternatively, at least one type of unsaturated carboxylic acid and at least one type of acid anhydride may be used. In the following description, when the tackifier (B) contains a reaction product of an unsaturated carboxylic acid or acid anhydride with rosin, it may be described as "the tackifier (B) is carboxylic acid-modified," "the tackifier (B) is carboxylic acid-modified," etc. On the other hand, when the tackifier (B) does not contain a reaction product of an unsaturated carboxylic acid or acid anhydride with rosin, it may be described as "the tackifier (B) is not carboxylic acid-modified," "the tackifier (B) is not carboxylic acid-modified," etc.

[0078] Examples of terpene phenolic resins include hydrogenated terpene phenolic resins. The tackifier (B) preferably contains at least one selected from the group consisting of rosin resins, rosin ester resins, reaction products of unsaturated carboxylic acids or acid anhydrides with rosin (rosin resins or rosin ester resins), terpene phenolic resins, and alicyclic petroleum resins. More preferably, the tackifier (B) is at least one selected from the group consisting of rosin ester resins, reaction products of unsaturated carboxylic acids or acid anhydrides with rosin (rosin resins or rosin ester resins), and terpene phenolic resins, with rosin ester resins or reaction products of unsaturated carboxylic acids or acid anhydrides with rosin (rosin resins or rosin ester resins) being particularly preferred. The rosin resins and rosin ester resins used in the tackifier (B) are different from alkali metal salts of rosin acid.

[0079] Although the tackifier (B) is generally added by mixing an emulsion of the tackifier (B) with the chloroprene latex (A), the tackifier (B) itself may be added during the production process of the chloroprene latex (A). This addition method is effective as one of the methods for adding a type of tackifier (B) whose emulsion is not commercially available.

[0080] Commercially available tackifiers (B) include rosin emulsions such as Super Ester NS-125 manufactured by Arakawa Chemical Industries, Ltd., E-720W manufactured by Taiwan Arakawa Chemical Industries, Ltd., Hariestar SK-218NS, Hariestar SK-323NS, Hariestar SK-370N, Hariestar SK-508H, and Hariestar SK-816E manufactured by Harima Chemical Industries, Ltd., and terpene phenol resin emulsions such as Tamanol (registered trademark) E-100, Tamanol (registered trademark) E-200NT, Tamanol (registered trademark) E-102A, and Tamanol (registered trademark) E-300NT manufactured by DRT Co., Ltd., and Dermulsene TR-602, etc. Examples of solid tackifiers (B) include alicyclic petroleum resins such as Alcon (registered trademark) M-135 manufactured by Arakawa Chemical Industries, Ltd.

[0081] <Chloroprene Latex Composition (X)> The chloroprene latex composition (X) contains the chloroprene latex (A) and the tackifier (B). The chloroprene latex composition (X) may contain other components as appropriate in addition to the chloroprene latex (A) and the tackifier (B).

[0082] [Other Components That May Be Included in Chloroprene Latex Composition (X)] If necessary, the chloroprene latex composition (X) may further contain, as long as the adhesive performance is not impaired, a polymer other than a chloroprene-based polymer, a pH adjuster (C), an antioxidant, a thickener, a plasticizer, an acid acceptor (e.g., zinc oxide, hydrotalcite), a filler (e.g., calcium carbonate, clay), a wetting agent, a crosslinking agent (e.g., polyisocyanate, polyglycidyl ether), etc. One or more of these other components may be used.

[0083] Examples of polymers other than the chloroprene polymer that can be contained in the chloroprene latex composition (X) include chlorinated polyolefin resins and (meth)acrylic polymers, but preferably, the chloroprene latex composition (X) does not contain a chlorinated polyolefin resin. When the chloroprene latex composition (X) contains a (meth)acrylic polymer, the content of the (meth)acrylic polymer is preferably less than 30 parts by mass, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the solids content of the chloroprene latex (A). It is particularly preferable that the chloroprene latex composition (X) does not contain a (meth)acrylic polymer.

[0084] The type of pH adjuster (C) that can be contained in the chloroprene latex composition (X) is not particularly limited, but the pH adjuster (C) is preferably a weak acid having at least one logarithm of the reciprocal of its acid dissociation constant (pKa) at 25° C. of preferably 8.0 to 11.0, more preferably 9.0 to 10.0. The upper and lower limits of the pKa of the pH adjuster (C) may be in any combination.

[0085] The pH adjuster (C) may be at least one selected from the group consisting of amino acids, organic acids, and inorganic weak acids. Examples of amino acids used as the pH adjuster (C) include glycine, aspartic acid, alanine, glutamic acid, valine, glutamine, leucine, arginine, isoleucine, lysine, serine, histidine, threonine, phenylalanine, cysteine, methionine, tryptophan, asparagine, and proline. Examples of organic acids used as the pH adjuster (C) include citric acid, acetic acid, and formic acid. Examples of inorganic weak acids used as the pH adjuster (C) include boric acid. One or more pH adjusters (C) may be used. Particularly preferably, the pH adjuster (C) is at least one selected from the group consisting of glycine and boric acid.

[0086] When the chloroprene latex composition (X) contains a pH adjuster (C), the initial adhesive strength and heat resistance of a layer containing a solid content prepared by drying the chloroprene latex composition (X) tend to be good. When the chloroprene latex composition (X) contains a pH adjuster (C), the initial adhesive strength of the adhesive layer tends to be good even when the drying time is so short that the adhesive layer is not sufficiently dried (i.e., when the dispersion medium remains in the adhesive layer containing the solid content of the chloroprene latex composition (X)).

[0087] When a pH adjuster (C) is used, the product of the amount [mmol] of the pH adjuster (C) used per 100 grams (100 g) of solids of the chloroprene latex (A) and the valence of the pH adjuster (C) is preferably 30 mmol or less, more preferably 20 mmol or less, and even more preferably 15 mmol or less. When a pH adjuster (C) is used, the product of the amount [mmol] of the pH adjuster (C) used per 100 grams of solids of the chloroprene latex (A) and the valence of the pH adjuster (C) is preferably 0.1 mmol or more, more preferably 0.2 mmol or more, even more preferably 0.3 mmol or more, and even more preferably 0.5 mmol. The product of the amount [mmol] of the pH adjuster (C) used per 100 grams of solids of glycine is the amount of glycine used in mmoles in the case of glycine, a monovalent weak acid, and is three times the amount of citric acid used in mmoles in the case of citric acid, a trivalent acid. The upper and lower limits of the product of the amount of the pH adjuster (C) used and the valence may be any combination.

[0088] [Method for Producing Chloroprene Latex Composition (X)] The chloroprene latex composition (X) is produced by mixing the chloroprene latex (A), the tackifier (B), and, if necessary, the other components. The order of adding the components during mixing is not particularly limited.

[0089] [Physical Properties of Chloroprene Latex Composition (X)] The amount of solids in the chloroprene latex composition (X) is preferably 40% by mass or more, more preferably 43% by mass or more, and even more preferably 45% by mass or more, based on 100% by mass of the chloroprene latex composition (X). The amount of solids in the chloroprene latex composition (X) is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 58% by mass or less, based on 100% by mass of the chloroprene latex composition (X). The upper and lower limits of the amount of solids in the chloroprene latex composition (X) may be any combination. When the amount of solids in the chloroprene latex composition (X) is within the above range, the initial adhesive strength, state adhesive strength, and heat resistance tend to be good. Furthermore, the contact strength tends to be good, particularly even when the drying time after application to an adherend is short and the water in the chloroprene latex composition (X) applied to the surface of the adherend does not completely evaporate.

[0090] When a first layer obtained by applying chloroprene latex composition (X) to at least a part of a first adherend and drying under the drying conditions described below and a second layer containing solids obtained by applying chloroprene latex composition (X) to at least a part of a second adherend and drying under the drying conditions described below are bonded together under the bonding conditions described below, the adhesive strength (initial adhesive strength) 5 minutes after bonding is preferably 1.5 kN / m or more, more preferably 1.8 kN / m or more, even more preferably 2.0 kN / m or more, and particularly preferably 2.5 kN / m or more. The upper limit of the initial adhesive strength is not particularly limited, but is usually 4.0 kN / m. Here, the amount of the solids of chloroprene latex composition (X) attached to both the first adherend and the second adherend is 50 g / m. ２ In addition, when an adherend such as a fabric is used that contains voids into which the chloroprene latex composition (X) can penetrate, the adhesion amount of the solid content of the chloroprene latex composition (X) after the chloroprene latex composition (X) has penetrated into the voids of the adherend is set to 50 g / m. ２Both the first layer and the second layer are layers containing the solid content of the chloroprene latex composition (X), but may contain a dispersion medium derived from the chloroprene latex composition (X).

[0091] (Drying conditions) Drying conditions are 23°C, 50% relative humidity, and 10 minutes of drying. (Adhesion conditions) The first layer and the second layer are brought into contact with each other, set in a small press, and pressed at 5 MPa for 3 minutes. The pressing environment is 23°C, 50% relative humidity.

[0092] A first layer obtained by applying chloroprene latex composition (X) to at least a portion of a first adherend and drying under the drying conditions described above and a second layer obtained by applying chloroprene latex composition (X) to at least a portion of a second adherend and drying under the drying conditions described above are bonded together under the above-mentioned bonding conditions, and then aged for 24 hours at 23°C and 50% relative humidity. The adhesive strength (normal adhesive strength) of a test specimen obtained by this is preferably 4.0 kN / m or more, more preferably 4.5 kN / m or more, and even more preferably 5.0 kN / m or more. The upper limit of the normal adhesive strength is not particularly limited, but is usually 7.0 kN / m. Here, the amount of solids of chloroprene latex composition (X) applied to both the first adherend and the second adherend is 50 g / m. ２ In addition, when an adherend such as a fabric is used that contains voids into which the chloroprene latex composition (X) can penetrate, the adhesion amount of the solid content of the chloroprene latex composition (X) after the chloroprene latex composition (X) has penetrated into the voids of the adherend is set to 50 g / m. ２ Both the first layer and the second layer are layers containing the solid content of the chloroprene latex composition (X), but may contain a dispersion medium derived from the chloroprene latex composition (X).

[0093] The heat resistance temperature of the test specimen (i.e., one cured for 24 hours after bonding) is determined using an apparatus in which the first adherend is hung in an oven by a hook attached to one corner, and a 1 kg weight is hung from the second adherend, both of which are hung in the oven as shown in FIG. 2. Specifically, with the test specimen placed as shown in FIG. 2, the temperature in the oven is increased at a rate of 0.4°C / min, and the temperature at which the second adherend is completely peeled from the first adherend is taken as the heat resistance temperature of the chloroprene latex composition (X). The heat resistance temperature is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher. There are no particular limitations on the upper limit of the heat resistance temperature, but it is usually 120°C.

[0094] The amount of the dispersion medium in the layer containing solids obtained by applying the chloroprene latex composition (X) to at least a part of an adherend in the amount described below and drying under the drying conditions described below is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, relative to 100% by mass of the layer containing solids. The lower limit of the amount of the dispersion medium in the layer containing solids is not particularly limited, but is usually 0.001% by mass.

[0095] (Deposition amount) The deposition amount of the solid content of the chloroprene latex composition (X) was 50 g / m ２ In addition, when an adherend such as a fabric is used that contains voids into which the chloroprene latex composition (X) can penetrate, the adhesion amount of the solid content of the chloroprene latex composition (X) after the chloroprene latex composition (X) has penetrated into the voids of the adherend is set to 50 g / m. ２ (Drying Conditions) The drying conditions are 23°C and 50% relative humidity for 10 minutes.

[0096] Adhesives and Adhesive Products The chloroprene latex composition (X) is used as an adhesive. The chloroprene latex composition (X) is applied to a part or the entire surface of an adherend, and the chloroprene latex composition (X) is dried on the surface of the adherend to form a layer containing the solid content of the chloroprene latex composition (X), thereby obtaining an adherend with an adhesive layer. That is, the layer containing the solid content of the chloroprene latex composition (X) serves as the adhesive layer. Here, the layer containing the solid content does not need to be completely dry, and may be in a state containing the solid content and a dispersion medium such as water. Examples of adherends include urethane foam, foams, sheets, films, canvas, glass, and any other material to which the chloroprene latex composition (X) can be adhered.

[0097] A bonded product can also be produced by laminating multiple adherends via the chloroprene latex composition (X). The multiple adherends may be the same type, or one adherend (hereinafter also referred to as the "first adherend") may be a different type from the other adherend (hereinafter also referred to as the "second adherend"). When producing a bonded product, a layer containing the solid content of the chloroprene latex composition (X) is provided on each of the multiple adherends to be bonded, and then the layers of the adherends are brought into contact with each other to bond them, thereby producing a bonded product. Examples of bonded products include furniture and shoes.

[0098] <<Method for Producing Bonded Product>> A bonded product can be suitably produced, for example, by the following production method. That is, a bonded product can be produced by a method including: (1) a step of adhering chloroprene latex composition (X) to at least a portion of each of a first adherend and a second adherend; (2) a step of drying the chloroprene latex composition (X) adhered to the first adherend and the chloroprene latex composition (X) adhered to the second adherend to form a layer containing a solid content of the chloroprene latex composition (X); and (3) a step of bonding the layer formed on the first adherend and the layer formed on the second adherend by contacting them with each other.

[0099] <Step (1)> An example of a treatment performed in the step (step (1)) of adhering the chloroprene latex composition (X) to an adherend will be described below. As a method for adhering the chloroprene latex composition (X) to an adherend, any method capable of bringing the adherend into contact with the chloroprene latex composition (X) can be used. For example, the chloroprene latex composition (X) may be applied to the surface of the adherend, or the adherend may be partially immersed in a container containing the chloroprene latex composition (X). Furthermore, the chloroprene latex composition (X) may be dropped onto the surface of the adherend. More specific examples of the method include application using a brush or paintbrush, spraying, screen printing, flow coating, spin coating, and dipping, and application to a roll or a flat plate using a bar coater, a T-die, a T-die with a bar, a doctor knife, a roll coater, a die coater, or the like. The adhesion area of ​​the chloroprene latex composition (X) may be the entire surface or a part of the surface of either the first adherend or the second adherend.

[0100] <Step (2)> In step (2), the chloroprene latex composition (X) deposited in step (1) is dried to form a layer containing the solid content of the chloroprene latex composition (X). The thickness of the layer containing the solid content is not particularly limited as long as the initial adhesive strength and normal adhesive strength are obtained, but is preferably about 20 to 100 μm. The drying time is not particularly limited as long as a layer containing the solid content can be formed, but is preferably 5 minutes or more, more preferably 8 minutes or more, and preferably 60 minutes or less, more preferably 45 minutes or less. The upper and lower limits of the drying temperature may be any combination. The drying temperature is also not particularly limited as long as a layer containing the solid content can be formed, but is preferably 10 to 90°C, more preferably 15 to 80°C.

[0101] The term "drying" as used herein does not only mean complete removal of the dispersion medium from the chloroprene latex composition (X), but also includes removal of the dispersion medium to an extent that the solid content in the chloroprene latex composition (X) can be formed into a layer. Specifically, the term "drying" includes removal of the dispersion medium until the amount of the dispersion medium in the layer containing the solid content is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, relative to 100% by mass of the layer containing the solid content. Furthermore, the term "drying" as used herein does not particularly limit the lower limit of the amount of the dispersion medium in the layer containing the solid content after drying, but is usually 0.001% by mass.

[0102] <Step (3)> In step (3), the layer containing solids formed on the surface of the first adherend and the layer containing solids formed on the surface of the second adherend are brought into contact with each other and bonded together. As a result, the first adherend and the second adherend are bonded together. Pressure may be applied to strengthen the bond between the layer containing solids formed on the surface of the first adherend and the layer containing solids formed on the surface of the second adherend. Pressure may be applied to the entire bonded product, or may be applied only to the portions of the first and second adherends where the layer containing solids is provided. There are no particular limitations on the method of applying pressure, and there are also no particular limitations on the pressure, as long as it is a pressure that does not significantly deform the layer containing solids and the adherends.

[0103] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, a chloroprene latex that does not fall under the category of chloroprene latex (A) may be referred to as chloroprene latex (cA). Similarly, a tackifier that does not fall under the category of tackifier (B) may be referred to as tackifier (cB), and a chloroprene latex composition that does not fall under the category of chloroprene latex composition (X) may be referred to as chloroprene latex composition (cX). Physical properties were measured using the following methods.

[0104] <Methods for Measuring Physical Properties> [Method for Calculating Polymerization Conversion Rate] After the initiation of polymerization of the chloroprene polymer, the emulsion was collected, weighed, and dried by standing in an oven at 100°C for 2 hours to obtain a dried product. The dried product obtained by the drying process contained the chloroprene polymer and solids other than the chloroprene polymer. Therefore, the amount of components that do not volatilize at 100°C among the various components used in the emulsion polymerization was calculated from the amounts charged during polymerization and the mass of the collected emulsion, and this was used as the mass of the solids other than the chloroprene polymer. The mass of the dried product obtained by drying the emulsion after the initiation of polymerization minus the mass of the solids other than the chloroprene polymer was used as the "amount of chloroprene polymer produced," and the polymerization conversion rate was calculated according to formula (3). Polymerization conversion rate [%] = [(amount of chloroprene polymer produced) / (amount of all monomers charged)] × 100 (3)

[0105] [Ratio of Tetrahydrofuran Insoluble Content] 1 g of chloroprene latex (A) was dropped into 100 ml of tetrahydrofuran, and the mixture was shaken overnight. The supernatant solution phase was then separated using a centrifuge. The shaking and centrifugation were carried out at 25°C. The resulting solution phase was heated to 100°C, and the tetrahydrofuran was evaporated over 1 hour. The mass of the dried product was measured. This gives the mass of the chloroprene polymer dissolved in the solution phase.

[0106] The content of the tetrahydrofuran-insoluble portion of the chloroprene polymer that does not dissolve in tetrahydrofuran at 25°C (tetrahydrofuran insoluble portion) was calculated by substituting the mass of the chloroprene polymer in 1 g of chloroprene latex (A) and the mass of the soluble portion into formula (4). Tetrahydrofuran insoluble portion (mass%) = {1 - [(mass of soluble portion) / (mass of chloroprene polymer in 1 g of chloroprene latex (A)]} × 100 (4) In formula (4), the mass of the chloroprene polymer in 1 g of chloroprene latex (A) was considered to be the mass of the solid portion obtained by drying 1 g of chloroprene latex (A). When drying chloroprene latex (A), it was dried by leaving it to stand in an oven at 100°C for 2 hours. The tetrahydrofuran insoluble content of the chloroprene latex (cA) was also determined in the same manner as in the chloroprene latex (A).

[0107] [Melt Enthalpy of Chloroprene Polymer] 1 g of chloroprene latex (A) was weighed into an aluminum dish with a diameter of 4 cm and dried in an oven at 141°C for 15 minutes to obtain a dried product. Approximately 10 mg of the dried product was collected as a sample, sealed in a DSC measurement pan, and measured using a differential scanning calorimeter (DSC7020 manufactured by SII) under the following measurement conditions. The obtained DSC curve was analyzed under the following analysis conditions to determine the melting enthalpy.

[0108] (Measurement Conditions) A DSC measurement pan containing a sample was heated to 60°C and held at 60°C for 10 minutes to melt the crystals in the sample. Next, the temperature was lowered to 3°C at a cooling rate of 10°C / min and the sample was held at 3°C ​​for 360 minutes to crystallize the chloroprene polymer in the sample. Thereafter, the sample was heated to 80°C at a heating rate of 10°C / min to melt the crystals of the chloroprene polymer.

[0109] (Analysis Method) The slope of the DSC curve (thermal profile) obtained by DSC measurement was corrected so that the fluctuation in the calorific value within the range of 50 to 60°C, which is equal to or higher than the crystalline melting temperature of the chloroprene polymer, was within 2 mW. The flat region between 50 and 60°C was used as a baseline and extended toward lower temperatures, and the crystalline melting enthalpy of chloroprene was calculated from the area of ​​the peak surrounded by the baseline and the DSC curve. The melting enthalpy of chloroprene latex (cA) was also determined by the same method as for chloroprene latex (A).

[0110] [Z-average particle size] First, each of the emulsions of chloroprene latex (A) or tackifier (B) used in the examples and comparative examples was diluted with pure water to 0.01 to 0.1 mass %. The z-average particle size of each of the obtained solutions was measured using a dynamic light scattering photometer (ZETASIZER (registered trademark) Nano-S, manufactured by Malvern Panalytical Ltd.). The z-average particle size of the chloroprene latex (cA) and the tackifier (cB) was also determined by the same method as for the chloroprene latex (A).

[0111] [Method for measuring the softening point of tackifier (B)] 5 g of tackifier (B) was added to 100 mL of tetrahydrofuran and dissolved by shaking for 10 hours using a shaker (SA300) manufactured by Yamato Scientific Co., Ltd. The solution after shaking was added dropwise to 500 mL of methanol, and the resulting coagulated material was filtered through a stainless steel mesh with a mesh size of 80 and dried overnight in a desiccator. The obtained dried coagulated material was measured using the ring and ball method in accordance with JIS K 5902. The sample was melted at low temperature without forming bubbles, and after melting, the sample was filled into a ring preheated to an appropriate temperature and then the softening point was measured using an automatic softening point evaluation device in a glycerin bath.

[0112] <Preparation of Chloroprene Latex> [Production Example 1: Preparation of Chloroprene Latex (A-1)] A 60-liter reactor was charged with 20.0 kg of 2-chloro-1,3-butadiene (chloroprene), 20 g of n-dodecyl mercaptan, 18 kg of pure water, 700 g of disproportionated rosin acid (R-600, manufactured by Arakawa Chemical Industries, Ltd.), 180 g of sodium hydroxide, and 120 g of a sodium salt of a β-naphthalenesulfonic acid formalin condensate. When the total amount of all the monomers charged was 100 parts by mass, the amount of n-dodecyl mercaptan charged was 0.1 parts by mass. The starting materials charged in the reactor were emulsified, and the disproportionated rosin acid was converted into a rosin soap.

[0113] Potassium persulfate was added as an initiator to an emulsion obtained by emulsifying the starting materials, and polymerization was carried out at 20°C under a nitrogen atmosphere. When the polymerization conversion reached 75% by mass, an emulsion of phenothiazine was immediately added to terminate the polymerization. Subsequently, unreacted monomers were removed by steam distillation, and the resulting mixture was concentrated to a solids concentration of 57% by mass, thereby obtaining a chloroprene latex (A-1) containing a chloroprene polymer. The tetrahydrofuran-insoluble content of the chloroprene polymer in the chloroprene latex (A-1) was 0% by mass, the fusion enthalpy was 22 mJ / mg, and the z-average particle size was 150 nm. The obtained values ​​are shown in Table 1-1. In the following description, Tables 1-1, 1-2, and 1-3 are collectively referred to as Table 1.

[0114] [Production Example 2: Preparation of Chloroprene Latex (A-2)] A 60-liter reactor was charged with 22.0 kg of 2-chloro-1,3-butadiene (chloroprene), 11 g of n-dodecyl mercaptan, 12.5 kg of purified water, 380 g of disproportionated rosin acid (R-600, manufactured by Arakawa Chemical Industries, Ltd.), 240 g of potassium hydroxide, and 105 g of sodium salt of β-naphthalenesulfonic acid formalin condensate. The amount of n-dodecyl mercaptan charged was 0.05 parts by mass, assuming a total of 100 parts by mass of all monomers charged. The starting materials charged in the reactor were emulsified, and the disproportionated rosin acid was converted into rosin soap. Potassium persulfate was added as an initiator to the emulsion obtained by emulsifying the starting materials, and polymerization was carried out at 40°C under a nitrogen atmosphere. When the polymerization conversion rate reached 90% by mass, an emulsion of phenothiazine was immediately added to terminate the polymerization. Subsequently, unreacted monomers were removed by steam distillation to obtain a chloroprene latex (A-2) containing a chloroprene polymer. The tetrahydrofuran-insoluble content of the chloroprene polymer in the chloroprene latex (A-2) was 86% by mass, the fusion enthalpy was 4.65 mJ / mg, and the z-average particle size was 210 nm.

[0115] [Production Examples 3 to 4: Preparation of chloroprene latexes (A-3) to (A-4)] Chloroprene latexes (A-3) to (A-4) were prepared in the same manner as in Production Example 2, except that the amount of n-dodecyl mercaptan charged and the polymerization conversion rate were set as shown in Table 1. The physical properties of the chloroprene latexes (A-3) to (A-4) are shown in Table 1.

[0116] Production Example 5: Preparation of Chloroprene Latex (A-5) A 60-liter reactor was charged with 18.8 kg of chloroprene, 1.2 kg of 2,3-dichloro-1,3-butadiene, 17 kg of pure water, 900 g of disproportionated rosin acid (R-600, manufactured by Arakawa Chemical Industries, Ltd.), 240 g of potassium hydroxide, and 50 g of the sodium salt of a β-naphthalenesulfonic acid formalin condensate. Here, assuming a total of 100 parts by mass of all monomers, the amount of chloroprene charged was 94 parts by mass, and the amount of 2,3-dichloro-1,3-butadiene charged was 6 parts by mass. Furthermore, assuming a total of 100 parts by mass of all monomers charged, the amount of n-dodecyl mercaptan charged was 0 parts by mass. The starting materials charged in the reactor were emulsified, and the disproportionated rosin acid was converted into a rosin soap.

[0117] Potassium persulfate was added as an initiator to an emulsion obtained by emulsifying the starting materials, and polymerization was carried out at 40°C under a nitrogen atmosphere. When the polymerization conversion reached 89% by mass, an emulsion of phenothiazine was immediately added to terminate the polymerization. Next, unreacted monomers were removed by steam distillation to obtain a chloroprene latex (A-5) containing a chloroprene polymer. The tetrahydrofuran-insoluble content of the chloroprene polymer in the chloroprene latex (A-5) was 85% by mass, the fusion enthalpy was 0.31 mJ / mg, and the z-average particle size was 130 nm. The obtained physical properties are shown in Table 1.

[0118] [Production Examples 6 to 8: Preparation of Chloroprene Latexes (A-6) to (A-8)] Chloroprene latex (A-1) obtained in Production Example 1 and chloroprene latex (A-5) obtained in Production Example 5 were mixed to prepare chloroprene latexes (A-6) to (A-8). The mixing ratio of the latexes was such that the mass of the solids of the chloroprene latex (A-1):the mass of the solids of the chloroprene latex (A-5)=25:75 for the chloroprene latex (A-6). In addition, in the chloroprene latex (A-7), the mass ratio of the solid contents of the chloroprene latex (A-1):the mass ratio of the solid contents of the chloroprene latex (A-5) was 50:50, and in the chloroprene latex (A-8), the mass ratio of the solid contents of the chloroprene latex (A-1):the mass ratio of the solid contents of the chloroprene latex (A-5) was 75:25. The physical properties obtained for the chloroprene latexes (A-6) to (A-8) are shown in Table 1.

[0119] [Production Examples 9 and 10: Preparation of chloroprene latexes (cA-1) and (cA-2)] Chloroprene latexes (cA-1) and (cA-2) were prepared in the same manner as in Production Example 5, except that the ratios of the monomers charged as starting materials, the amount of n-dodecyl mercaptan charged, and the polymerization conversion rates were set as shown in Table 1. The physical properties obtained for the chloroprene latexes (cA-1) and (cA-2) are shown in Table 1.

[0120] Production Example 11: Preparation of Chloroprene Latex (cA-3) A 60-liter reactor was charged with 19.6 kg of chloroprene, 400 g of methacrylic acid, 80 g of n-dodecyl mercaptan, 21 kg of pure water, and 700 g of polyvinyl alcohol (PVA). Here, assuming a total of 100 parts by mass of all monomers, the amount of chloroprene charged was 98 parts by mass, and the amount of methacrylic acid charged was 2 parts by mass. Furthermore, assuming a total of 100 parts by mass of all monomers charged, the amount of n-dodecyl mercaptan charged was 0.4 parts by mass. The starting materials charged in the reactor were emulsified, and the disproportionated rosin acid was converted into rosin soap.

[0121] Potassium persulfate was added as an initiator to an emulsion obtained by emulsifying the starting materials, and polymerization was carried out at 40°C under a nitrogen atmosphere. When the polymerization conversion rate reached 100% by mass, an emulsion of phenothiazine was added to terminate the polymerization. Next, unreacted monomers were removed by steam distillation to obtain a chloroprene latex (cA-3) containing a chloroprene polymer. The tetrahydrofuran-insoluble content of the chloroprene polymer in the chloroprene latex (cA-3) was 43% by mass, the fusion enthalpy was 0.23 mJ / mg, and the z-average particle size was 420 nm.

[0122] [Production Example 12: Preparation of chloroprene latex (cA-4)] A chloroprene latex (cA-4) was prepared in the same manner as in Production Example 5, except that the ratio of each monomer charged as a starting material, the amount of n-dodecyl mercaptan charged, and the polymerization conversion rate were changed as shown in Table 1. The physical properties obtained for the chloroprene latex (cA-4) are shown in Table 1.

[0123] [Production Example 13: Preparation of chloroprene latex (cA-5)] A chloroprene latex (cA-5) was prepared in the same manner as in Production Example 2, except that the amount of n-dodecyl mercaptan charged and the polymerization conversion rate in Production Example 2 were changed as shown in Table 1. The physical properties obtained for the chloroprene latex (cA-5) are shown in Table 1.

[0124] [Production Examples 14 to 16: Preparation of chloroprene latexes (A-9) to (A-11)] Chloroprene latexes (A-9) to (A-11) were prepared in the same manner as in Production Example 2, except that the ratio of the charged amounts of each monomer, the charged amount of n-dodecyl mercaptan, and the polymerization conversion rate in Production Example 2 were changed as shown in Table 1. The physical properties obtained for the chloroprene latexes (A-9) to (A-11) are shown in Table 1.

[0125] [Production Example 17: Preparation of chloroprene latex (A-12)] Chloroprene latex (A-1) obtained in Production Example 1 and chloroprene latex (A-11) obtained in Production Example 16 were mixed to prepare chloroprene latex (A-12). The mixing ratio of the latexes was set to (mass of solids of chloroprene latex (A-1)): (mass of solids of chloroprene latex (A-11)) = 50:50. The physical properties obtained for chloroprene latex (A-12) are shown in Table 1.

[0126] [Production Example 18: Preparation of chloroprene latex (A-13)] A chloroprene latex (A-13) was prepared in the same manner as in Production Example 1, except that the ratio of the charged amounts of each monomer, the charged amount of n-dodecyl mercaptan, and the polymerization conversion rate in Production Example 1 were changed as shown in Table 1, and the concentration treatment was not performed. The physical properties obtained for the chloroprene latex (A-13) are shown in Table 1.

[0127] [Production Example 19: Preparation of chloroprene latex (A-14)] Chloroprene latex (A-5) obtained in Production Example 5 and chloroprene latex (A-13) obtained in Production Example 18 were mixed to prepare chloroprene latex (A-14). The mixing ratio of the latexes was set to (mass of solids of chloroprene latex (A-5)):(mass of solids of chloroprene latex (A-13))=50:50. The physical properties obtained for chloroprene latex (A-14) are shown in Table 1.

[0128] For each of the obtained chloroprene latexes (A-1) to (A-10), (A-12), (A-14), and (cA-1) to (cA-5), the Log β value calculated from the melting enthalpy β (mJ / mg) of the chloroprene polymer was plotted against the tetrahydrofuran-insoluble content of the chloroprene polymer, as shown in Figure 1. The straight line in Figure 1 is the line represented by formula (1). As shown in Figure 1, all of the chloroprene latexes (A-1) to (A-10), (A-12), and (A-14) satisfied formula (1). On the other hand, all of the chloroprene latexes (cA-1) to (cA-5) did not satisfy formula (1).

[0129]

[0130]

[0131]

[0132] <Raw Materials> The following materials were used in the following Examples and Comparative Examples. [Chloroprene Latex] Chloroprene latexes (A-1) to (A-10), (A-12), (A-14), (cA-1) to (cA-5) produced in the above Production Examples 1 to 15, 17, and 19.

[0133] [Tackifiers] "Tackifier (B-1)": Rosin-based emulsion (Harima Chemicals Co., Ltd., Hariestar SK-370N, softening point = 100°C, solid content 50% by mass, z-average particle size = 450 nm, containing a reaction product of unsaturated carboxylic acid and rosin) "Tackifier (B-2)": Rosin-based emulsion (Harima Chemicals Co., Ltd., Hariestar SK-816E, softening point = 145°C, solid content 50% by mass, z-average particle size = 270 nm, containing no reaction product of unsaturated carboxylic acid and rosin) "Tackifier (B-3)": Rosin-based emulsion (Arakawa Chemical Industries, Ltd., Superester NS-125, softening point = 125°C, solid content 50% by mass, z-average particle size = 440 nm, containing a reaction product of unsaturated carboxylic acid and rosin)

[0134] "Tackifier (cB-1)": Rosin-based emulsion (Kraton Polymers, Aquatac 2680, softening point = 80°C, solid content 54% by mass, z-average particle size = 280 nm, does not contain reaction products of unsaturated carboxylic acid and rosin) "Tackifier (cB-2)": Rosin-based emulsion (Arakawa Industries, Ltd., Tamanol E-900NT, softening point = 160°C, solid content 54% by mass, z-average particle size = 270 nm, does not contain reaction products of unsaturated carboxylic acid and rosin) "Tackifier (cB-3)": Rosin-based emulsion (Harima Chemicals, Ltd., Hariestar SK-822E, softening point = 170°C, solid content 50% by mass, z-average particle size = 270 nm, does not contain reaction products of unsaturated carboxylic acid and rosin)

[0135] [pH adjuster (C)] "pH adjuster (C-1)": glycine (manufactured by Resonac Co., Ltd.), pKa ２ = 9.6 "pH adjuster (C-2)": boric acid (manufactured by Kanto Chemical Co., Inc.), pKa = 9.2. Note that both glycine and boric acid are monovalent weak acids.

[0136] Example 1 Preparation of Chloroprene Latex Composition (X-1) A tackifier (B-1) was added to chloroprene latex (A-1) in an amount such that the amount of the solid content of the tackifier (B-1) was 30 parts by mass relative to 100 parts by mass of the solid content of the chloroprene latex (A-1), to prepare a chloroprene latex composition (X-1).

[0137] [Preparation of test pieces for evaluating adhesive strength] Two pieces of No. 6 canvas (25 mm width x 150 mm length, coating surface 25 mm width x 100 mm length) were coated with 100 g (solid content) / m ２ The chloroprene latex composition (X-1) was applied with a brush and dried for 30 minutes under conditions of 23°C and 50% relative humidity. Thereafter, the chloroprene latex composition (X-1) was again applied at an amount of 50 g (solid content) / m ２ After application, the mixture was dried for 10 minutes under conditions of 23°C and 50% relative humidity to obtain an adherend having a layer containing the solid content of the chloroprene latex composition (X-1) attached thereto. Two adherends were brought into contact with each other with the solid content layers facing each other, and then bonded together using a small press at a pressure of 5 MPa for 3 minutes to obtain a test piece for evaluating adhesive strength.

[0138] [Initial Adhesion] The prepared test pieces for evaluating adhesive strength were aged for 2 minutes under conditions of 23°C and 50% relative humidity (i.e., 5 minutes after application, including the time for pressing with a small press), and the initial adhesion (kN / m) was measured according to a method in accordance with JIS K 6854-3-1999. The peel speed was 200 mm / min. The obtained initial adhesion was evaluated according to the following evaluation criteria. The obtained initial adhesion and the evaluation results are shown in Table 2-1. In the following description, Table 2-1 and Table 2-2 are collectively referred to as Table 2. (Evaluation Criteria) SS: The initial adhesion was 2.5 kN / m or more. AA: The initial adhesion was 1.5 kN / m or more but less than 2.5 kN / m. CC: The initial adhesion was less than 1.5 kN / m.

[0139] [Normal Adhesion Strength] Test pieces for adhesive strength evaluation were aged for 24 hours under conditions of 23°C and 50% relative humidity, and the adhesive strength was measured according to a method in accordance with JIS K 6854-3-1999, and recorded as normal adhesive strength (kN / m). The peel speed was 200 mm / min. The normal adhesive strength obtained was further evaluated according to the following evaluation criteria. The normal adhesive strengths obtained and the evaluation results are shown in Table 2. (Evaluation Criteria) SS: The normal adhesive strength was 5.0 kN / m or more. AA: The normal adhesive strength was 4.0 kN / m or more but less than 5.0 kN / m. CC: The normal adhesive strength was less than 4.0 kN / m.

[0140] [Heat Resistance Test] After aging the test specimen for adhesive strength evaluation under conditions of 23°C and 50% relative humidity for 24 hours, it was cut into a 25mm x 25mm adhesive-coated portion and a 25mm x 25mm non-adhesive-coated portion to prepare a 25mm x 50mm heat resistance test specimen. A hook was attached to one end of the non-adhesive portion of the heat resistance test specimen, and the heat resistance test specimen was hung in an oven set to 40°C, with a 1kg weight attached to the other end of the non-adhesive portion. An example of the heat resistance test specimen hanging in the oven is shown in Figure 2. After maintaining the oven temperature at 40°C for 30 minutes, the temperature was increased at a rate of 0.4°C / min. The temperature (°C) at which the adhesive surface of the heat resistance test specimen completely peeled off was recorded and used as the heat resistance temperature. The obtained heat resistance temperatures were evaluated according to the following evaluation criteria. The obtained heat resistance temperatures and their evaluation results are shown in Table 2. (Evaluation Criteria) SS: Heat resistant temperature was 70°C or higher. AA: Heat resistant temperature was 60°C or higher and lower than 70°C. CC: Heat resistant temperature was lower than 60°C.

[0141] Examples 2 to 8, 14 to 17, Comparative Examples 1 to 5 Preparation of chloroprene latex composition (X) or chloroprene latex composition (cX), preparation of test pieces, and tests using the test pieces were carried out in the same manner as in Example 1, except that the type of chloroprene latex used in preparing the chloroprene latex composition was changed as shown in Table 2. The obtained results are shown in Table 2.

[0142] <Measurement of the proportion of water contained in the layer containing solids> In measuring the proportion of water contained in the layer containing solids, the chloroprene latex composition (X-7) prepared in Example 7 was used as the chloroprene latex composition (X). A No. 6 canvas (25 mm wide x 150 mm long, coating surface 25 mm wide x 100 mm long) was coated with 100 g (solids) / m ２ The chloroprene latex composition (X-7) was applied with a brush, and dried under conditions of 23°C and 50% relative humidity for 1 hour. The weight (W １ Then, 50 g (solid content) / m of chloroprene latex composition (X-7) was again added to the obtained test piece. ２After coating, the coating was dried for 10 minutes under conditions of 23°C and 50% relative humidity to obtain a test piece having a layer containing the solid content of the chloroprene latex composition (X-7) attached thereto. The mass (W ｗｅｔ The test piece with the layer containing solids attached thereto was then left to stand in an oven at 100°C for 1 hour to completely dry the layer of solids, and the mass after drying (W ｄｒｙ The proportion of water contained in the layer containing solids was calculated using the following formula, and it was found that 30% by mass of the layer containing solids was water (dispersion medium) out of 100% by mass of the layer containing solids. Proportion of water contained in the layer containing solids [mass %] = ((W ｗｅｔ -W １ )-(W ｄｒｙ -W １ )) / (W ｗｅｔ -W １ ) × 100 In addition, since the drying conditions when the layer containing solids was prepared were similar in Examples other than Example 7, the proportion of water (dispersion medium) contained in the layer containing solids is considered to be about 30 mass % out of 100 mass % of the mass of the layer containing solids.

[0143] The amount of tackifier (B-1) is the amount (parts by mass) of the solid content of tackifier (B-1) relative to 100 parts by mass of the solid content of the chloroprene latex. Also, the "z-average particle size*" is the z-average particle size of the chloroprene latex.

[0144] The amount of tackifier (B-1) is the amount (parts by mass) of the solid content of tackifier (B-1) relative to 100 parts by mass of the solid content of the chloroprene latex. Also, the "z-average particle size*" is the z-average particle size of the chloroprene latex.

[0145] Example 9, Comparative Examples 6 to 8 Preparation of chloroprene latex compositions, preparation of test pieces, and tests using the test pieces were carried out in the same manner as in Example 1, except that the type of tackifier used in preparing the chloroprene latex composition was changed as shown in Table 3. The obtained results are shown in Table 3 together with the results of Example 1. In Table 3, when the tackifier contains a reaction product of an unsaturated carboxylic acid and a rosin, it is stated that the tackifier is carboxylic acid-modified. On the other hand, when the tackifier does not contain a reaction product of an unsaturated carboxylic acid and a rosin, it is stated that the tackifier is not carboxylic acid-modified.

[0146] Preparation of a chloroprene latex composition, preparation of a test piece, and tests using the test piece were carried out in the same manner as in Example 7, except that the type of tackifier used in preparing the chloroprene latex composition was changed as shown in Table 3. The obtained results are shown in Table 3 together with the results of Example 7.

[0147] The amount of tackifier is the amount (parts by mass) of the solid content of the tackifier relative to 100 parts by mass of the solid content of the chloroprene latex. Also, the "z-average particle size*" is the z-average particle size of the chloroprene latex.

[0148] Examples 10 to 13, Comparative Examples 9 and 10 Preparation of chloroprene latex compositions, preparation of test pieces, and tests using the test pieces were carried out in the same manner as in Example 7, except that the amount of tackifier (B) used in preparing the chloroprene latex composition was changed to the amount shown in Table 4 relative to 100 parts by mass of the solid content in the chloroprene latex (A). The obtained results are shown in Table 4 together with the results of Example 7.

[0149] The amount of tackifier (B-1) is the amount (parts by mass) of the solid content of tackifier (B-1) relative to 100 parts by mass of the solid content of the chloroprene latex. Also, the "z-average particle size*" is the z-average particle size of the chloroprene latex.

[0150] Example 18 100 grams of the solid content in the chloroprene latex (A-14) was defined as 100 parts by mass. To the chloroprene latex (A-14), a tackifier (B-1) was added in an amount such that the solid content of the tackifier (B-1) was 30 parts by mass relative to 100 parts by mass of the solid content in the chloroprene latex (A-14), and 0.06 parts by mass (i.e., 0.80 mmol) of a pH adjuster (C-1) was added to prepare a chloroprene latex composition (X-18). Test pieces were prepared and tests using the test pieces were conducted in the same manner as in Example 17, except that the chloroprene latex composition (X-18) was used instead of the chloroprene latex composition (X-17). The obtained results are shown in Table 5, along with the results of Example 17.

[0151] Examples 19 to 22 Preparation of chloroprene latex compositions, preparation of test specimens, and tests using the test specimens were carried out in the same manner as in Example 17, except that the amount and type of pH adjuster used in preparing the chloroprene latex composition were changed to the amounts shown in Table 5. That is, in all of Examples 19 to 22, 100 grams of solids in the chloroprene latex (A-14) was defined as 100 parts by mass. The obtained results are shown in Table 5.

[0152]

[0153] In Table 5, the numerical value in the column for tackifier (B-1) is the amount (parts by mass) of the solid content of tackifier (B-1) relative to 100 parts by mass of the solid content of the chloroprene latex. The amount of pH adjuster (C) in Table 5 is the amount per 100 parts by mass of the solid content of the chloroprene latex. In addition, "z-average particle size*" is the z-average particle size of the chloroprene latex.

Claims

1. A chloroprene latex composition (X) comprising: a chloroprene latex (A) containing a chloroprene polymer satisfying the following requirement (a-1); and a tackifier (B) having a softening point of 85 to 155°C as measured by the ring and ball method (based on the measurement method of JIS K 5902). (a-1) The tetrahydrofuran-insoluble content α [mass%] of 100 mass% of the chloroprene polymer and the melting enthalpy β [mJ / mg] of the chloroprene polymer as measured by differential scanning calorimetry (DSC) satisfy the following formula (1): Logβ≧−0.022×α+1.0 (1) 2. The chloroprene latex composition (X) according to claim 1, wherein the chloroprene latex (A) comprises: a first chloroprene latex containing a chloroprene polymer having a tetrahydrofuran insoluble fraction of 0 to 15% by mass and a fusion enthalpy of 10 to 40 [mJ / mg]; and a second chloroprene latex containing a chloroprene polymer having a tetrahydrofuran insoluble fraction of 70 to 98% by mass and a fusion enthalpy of 0 to 10 [mJ / mg].

3. The chloroprene latex composition (X) according to claim 2, wherein, based on 100% by mass of solids contained in the chloroprene latex (A), the content of solids derived from the first chloroprene latex is 1 to 99% by mass, and the content of solids derived from the second chloroprene latex is 99 to 1% by mass.

4. The chloroprene latex composition (X) according to claim 1, wherein the chloroprene latex (A) contains an anionic emulsifier.

5. The chloroprene latex composition (X) according to claim 4, wherein the anionic emulsifier is a rosinate salt.

6. The chloroprene latex composition (X) according to claim 1, wherein the tetrahydrofuran-insoluble content α [mass%] and the fusion enthalpy β [mJ / mg] further satisfy the following formula (2): Log β≦−0.006×α+1.7 (2) 7. The chloroprene latex composition (X) according to claim 1, wherein the tackifier (B) comprises a compound containing a carboxyl group.

8. The chloroprene latex composition (X) according to claim 7, wherein the tackifier (B) comprises a reaction product of an unsaturated carboxylic acid or acid anhydride with rosin.

9. The chloroprene latex composition (X) according to claim 8, wherein the unsaturated carboxylic acid or acid anhydride is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, and cinnamic acid.

10. The chloroprene latex composition (X) according to claim 1, containing 3 to 90 parts by mass of the tackifier (B) per 100 parts by mass of the solid content of the chloroprene latex (A).

11. The chloroprene latex composition (X) according to claim 1, wherein the amount of solids in the chloroprene latex composition (X) is 40 to 70 mass % when the mass of the chloroprene latex composition (X) is 100 mass %.

12. The chloroprene latex composition (X) according to claim 1, further comprising a pH adjuster (C).

13. The chloroprene latex composition (X) according to claim 12, wherein the pH adjuster (C) is at least one selected from the group consisting of amino acids, organic acids, and inorganic weak acids.

14. The chloroprene latex composition (X) according to claim 12, wherein the pH adjuster (C) is a weak acid having at least one logarithm of the reciprocal of its acid dissociation constant (pKa) at 25°C in the range of 8.0 to 11.

0.

15. The chloroprene latex composition (X) according to claim 12, wherein the product of the amount [mmol] of the pH adjuster (C) used per 100 grams of the solids content of the chloroprene latex (A) and the valence of the pH adjuster (C) is 0.1 to 30 mmol.

16. A method for producing an adhesive product, comprising: (1) a step of adhering the chloroprene latex composition (X) according to any one of claims 1 to 15 to at least a portion of each of a first adherend and a second adherend; (2) a step of drying the chloroprene latex composition (X) adhered to the first adherend and the chloroprene latex composition (X) adhered to the second adherend to form a layer containing a solid content of the chloroprene latex composition (X); and (3) a step of adhering the layer formed on the first adherend and the layer formed on the second adherend by bringing them into contact with each other.

Images