Chloroprene Latex Adhesive

Abstract

To provide a chloroprene latex adhesive which exerts adhesive strength as quickly as possible after being sprayed onto an adherend; enables easy removal of any residues that adhere to the surface after spraying; and is hard to separate and precipitate even if stored under a high temperature environment exceeding 40°C.SOLUTION: A chloroprene latex adhesive includes: total 150 pts.wt. of a chloroprene latex mixture (a) obtained by mixing 35-65 pts.wt. of a chloroprene latex (a1) having a toluene solution transparency of 4 cm or higher, and 85-115 pts.wt. of a chloroprene latex (a2) having a toluene solution transparency defined by the following of lower than 4 cm; 0.3-1.7 pts.wt. of a surface active agent; 6-17 pts.wt. of an antioxidant; and 8-22 pts.wt. of a styrene butadiene rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a chloroprene latex adhesive for bonding porous materials such as urethane foam together. [Background technology]

[0002] Conventionally, chloroprene latex adhesives have been known that are applied to one or both surfaces of a porous substrate, such as an adherend, using a spray gun or the like, and then the coated surfaces are bonded together; specifically, one-component chloroprene latex adhesives are known that are used to bond foam materials used in vehicle interiors, furniture such as seat chairs and sofas, bedding, pillows, etc., or to bond urethane foams together (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2000-219859 [Patent Document 2] Patent Publication No. 2017-222804 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Due to the nature of chloroprene latex adhesives, they do not exhibit adhesive strength immediately after spraying onto the adherend, but rather as the solvent evaporates. From the perspective of workability, it is desirable for adhesive strength to be exhibited as quickly as possible after spraying onto the adherend (hereinafter, the time from spraying until adhesive strength is exhibited is referred to as the open time).

[0005] On the other hand, when applying chloroprene latex adhesive with a spray gun, the adhesive ejected from the spray gun often splashes onto areas other than the adherend surface, landing on the worker's hands or arms. The adhered adhesive (hereinafter referred to as "adhesion") can be removed relatively easily before it dries, but once it dries, the adhesion solidifies on the surface, forming a so-called "sticky" state. Removing this stuck adhesion is not easy (hereinafter, this issue may be referred to as "removability").

[0006] Furthermore, chloroprene latex adhesives are sometimes stored in high-temperature environments where temperatures exceed 40°C. When conventional chloroprene latex adhesives are stored in such high-temperature environments, the contents tend to separate and settle, making them unusable. In such cases, conventionally, the adhesives have had to be transported to a cooler environment each time they are stored, which can be time-consuming (hereinafter, this issue may be referred to as "storability").

[0007] Incidentally, the applicant of the present application proposed the following chloroprene latex adhesive in Japanese Patent Application No. 2021-052526 as an invention to solve the above-mentioned removability problem (hereinafter referred to as the prior invention).

[0008] The solid content is 40-60%. 60 to 80 parts by weight of a chloroprene latex (a1) having a toluene-soluble transparency of 4 cm or more as defined below, and 20 to 40 parts by weight of a chloroprene latex (a2) having a toluene dissolution transparency of less than 4 cm as defined below, 100 parts by weight in total of a chloroprene latex mixture (a) obtained by mixing the above, 20 to 40 parts by weight of a benzoic acid-based plasticizer (b); 2 to 10 parts by weight of a pH adjuster, Contains chloroprene latex adhesive. Toluene solution transparency: Transparency (cm) measured according to JIS K 0102:2016 for a solution obtained by dissolving 1 part by weight of a resin film obtained by drying chloroprene latex resin at room temperature in 10 parts by weight of toluene.

[0009] The details of the "toluene dissolution transparency (cm)" will be described later.

[0010] Hereinafter, the chloroprene latex (a1) having a toluene-dissolved transparency of 4 cm or more may be abbreviated as "high-transparency latex (a1)", and the chloroprene latex (a2) having a toluene-dissolved transparency of less than 4 cm may be abbreviated as "low-transparency latex (a2)".

[0011] According to this prior invention, the adhesive composition contains a chloroprene latex mixture (a) obtained by mixing a high-transparency latex (a1) and a low-transparency latex (a2), and thus during application using a spray gun or the like, deposits adhering to surfaces other than the adherend surface can be easily removed, and sufficient adhesive strength is provided to the adherend.

[0012] However, even this prior invention left room for improvement in order to solve the above-mentioned storage stability problems. As described above, there were demands for a chloroprene latex adhesive to exhibit adhesive strength as quickly as possible after spraying onto an adherend, i.e., to have as short an open time as possible, to be easily removed even if any deposits stick to the adhesive surface after spraying, and to be resistant to separation and sedimentation even when stored in a high-temperature environment exceeding 40°C. [Means for solving the problem]

[0013] The present invention, which aims to solve the above problems, was made based on the above prior invention and by further improving it.

[0014] That is, the chloroprene latex adhesive of the present invention has: The solid content is 40-60%. 35 to 65 parts by weight of a chloroprene latex (a1) having a toluene dissolution transparency of 4 cm or more as defined below, and 85 to 115 parts by weight of a chloroprene latex (a2) having a toluene dissolution transparency of less than 4 cm as defined below, 150 parts by weight of a chloroprene latex mixture (a) obtained by mixing the above, 0.3 to 1.7 parts by weight of a surfactant; 6 to 17 parts by weight of an antioxidant; 8 to 22 parts by weight of styrene-butadiene rubber, 2. A chloroprene latex adhesive comprising: Toluene solution transparency: Transparency (expressed in cm) measured in accordance with JIS K 0102:2016 for a solution prepared by dissolving 1 part by weight of a resin film obtained by drying chloroprene latex resin at room temperature in 10 parts by weight of toluene.

[0015] As mentioned above, hereinafter, the chloroprene latex (a1) having a toluene-dissolved transparency of 4 cm or more may be abbreviated as "high-transparency latex (a1)", and the chloroprene latex (a2) having a toluene-dissolved transparency of less than 4 cm may be abbreviated as "low-transparency latex (a2)". [Effects of the Invention]

[0016] The chloroprene latex adhesive of the present invention contains a chloroprene latex mixture (a) obtained by mixing a high-transparency latex (a1) and a low-transparency latex (a2), and therefore, during application using a spray gun or the like, deposits adhering to surfaces other than the adherend surface can be easily removed, and the adhesive has sufficient adhesive strength on the adherend.

[0017] Furthermore, because it contains surfactants, antioxidants, and styrene-butadiene rubber, the open time is short when applying using a spray gun, etc., and any adhesions that have adhered to surfaces other than the adherend can be easily removed.The chloroprene latex adhesive also does not easily separate or settle even when stored in a high-temperature environment exceeding 40°C. [Brief explanation of the drawings]

[0018] [Figure 1] Front view of the substrate used for adhesiveness evaluation BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The high-transparency latex (a1) and the low-transparency latex (a2) used in the present invention are not particularly limited as long as they are chloroprene latexes having a solid content of 40 to 60%, and commercially available products can be used, such as Skyprene SL-360, SL-390, and SL-590 (all trade names) manufactured by Tosoh Corporation, and DISPERCOLL C84 (trade name) manufactured by Covestro.

[0020] Next, the "toluene dissolution transparency" according to the present invention will be explained below. Note that the "toluene dissolution transparency" is the same as in the above-mentioned prior invention.

[0021] Several chloroprene latexes with solid contents of 40 to 60% were prepared and dried at room temperature to obtain resin films. Next, 1 part by weight of each of these resin films was dissolved in 10 parts by weight of toluene (hereinafter referred to as the latex-toluene solution).

[0022] Next, fill a transparency meter specified in JIS K 0102:2016 "Industrial Wastewater Testing Method" with this latex-toluene solution and view the bottom of the transparency meter from the top. Then, let the solution flow out from the bottom opening until the double cross sign at the bottom of the transparency meter can be clearly identified for the first time, and read the water level (cm) of the latex-toluene solution when the double cross sign can be clearly identified for the first time. This reading is the "toluene solution transparency" (unit: cm) of chloroprene latex.

[0023] Among the chloroprene latexes whose toluene dissolution transparency is measured in this way, the one having a toluene dissolution transparency of 4 cm or more is defined as high transparency latex (a1), and the one having a toluene dissolution transparency of less than 4 cm is defined as low transparency latex (a2).

[0024] Next, 35 to 65 parts by weight of the high transparency latex (a1) and 85 to 115 parts by weight of the low transparency latex (a2) are mixed to make a total of 150 parts by weight to obtain 150 parts by weight of a chloroprene latex mixture (a).

[0025] Regarding the mixing ratio, for example, when the high-transparency latex (a1) is 35 parts by weight, 115 parts by weight of the low-transparency latex (a2) is mixed, and when the high-transparency latex (a1) is 65 parts by weight, 85 parts by weight of the low-transparency latex (a2) is mixed to make 150 parts by weight of the chloroprene latex mixture (a).

[0026] The surfactant may be a polyoxyethylene alkyl ether sulfate or sodium lauryl sulfate. Commercially available surfactants include, for example, Hitenol NF-08, Hitenol NF-13, and Hitenol NF-17 (trade names) manufactured by Daiichi Kogyo Yakuhin Co., Ltd., and Emal 2F-30, Emal D-3-D, and Ramdel E-1000A (trade names) manufactured by Kao Corporation.

[0027] As the antioxidant, an oligomer type (phenol type) antioxidant, etc., can be used. As a commercially available product, for example, Cellosol K-840 (trade name) manufactured by Chukyo Yushi Co., Ltd. can be used.

[0028] As the styrene-butadiene rubber, commercially available products such as L-7230, L-5930, L-2301, and L-3200 manufactured by Asahi Kasei Chemicals Corporation (trade names) can be used.

[0029] Furthermore, in the chloroprene latex adhesive of the present invention, a plasticizer, a pH adjuster, and a pigment may be appropriately added as needed.

[0030] As the benzoic acid-based plasticizer (b), commercially available products can be used, such as Adeka Cizer PN-6122 (trade name) manufactured by Adeka Corporation.

[0031] In order to increase the initial adhesive strength, the chloroprene latex adhesive of the present invention is preferably blended with a pH adjuster (c) to adjust the pH to the range of 7.0 to 10.0. The pH adjuster (c) can be glycine, alanine, phenylalanine, glutamic acid, or the like, and among these, glycine is preferably used.

[0032] Then, 150 parts by weight of the chloroprene latex mixture (a) is blended with 20 to 40 parts by weight of a benzoic acid-based plasticizer (b) and 2 to 10 parts by weight of a pH adjuster (c) to obtain the chloroprene latex adhesive of the present invention. [Example]

[0033] As chloroprene latex, Skyprene Latex SL-360 (solid content 50 to 54%) manufactured by Tosoh Corporation (trade name) and DISPERCOLL C84 (solid content 54.5 to 55.5%) manufactured by Covestro (trade name) were prepared, and their toluene dissolution transparency was measured as follows.

[0034] First, these chloroprene latexes were dried at room temperature to prepare resin films, and then 1 part by weight of each resin film was dissolved in toluene at a ratio of 10 parts by weight to obtain each latex-toluene solution.

[0035] Each latex-toluene solution was filled into an AS ONE Corporation transparency meter (product name: ST-30), and the toluene transparency of each solution was measured. The results are as follows:

[0036] SL-360: 4.0cm C84: 1.5cm From the above measurement results, SL-360 is designated as the high transparency latex (a1) of the example, and C84 is designated as the low transparency latex (a2) of the example.

[0037] Next, these high-transparency latex (a1) and low-transparency latex (a2) were mixed in the weight ratios shown in Tables 1 and 2 to prepare 150 parts by weight of each of the chloroprene latex mixtures (a) of Examples 1 to 8 and Comparative Examples 1 to 7.

[0038] Next, Adeka Cizer PN-6122 (trade name) manufactured by Adeka Corporation was prepared as a benzoic acid-based plasticizer (b), and glycine was prepared as a pH adjuster, and these were mixed in the weight ratios shown in Tables 1 and 2.

[0039] Furthermore, styrene-butadiene rubber L-7230 (trade name, manufactured by Asahi Kasei Chemicals Corporation) was added as shown in the table to obtain each chloroprene latex adhesive (hereinafter simply referred to as adhesive) of the examples and comparative examples.

[0040] The comparative examples were prepared for comparison with the examples under the following conditions.

[0041] Comparative Example 1: No surfactant, antioxidant, or SBR was added to the chloroprene latex mixture. Comparative Example 2: Adding only surfactant to chloroprene latex mixture Comparative Example 3: Adding only antioxidant to chloroprene latex mixture Comparative Example 4: Adding only SBR to a chloroprene latex mixture Comparative Example 5: A surfactant and an antioxidant were added to a chloroprene latex mixture, but no SBR was added. Comparative Example 6: A surfactant and SBR were added to a chloroprene latex mixture, but no antioxidant was added. Comparative Example 7: Antioxidant and SBR were added to the chloroprene latex mixture, but no surfactant was added.

[0042] The removability and adhesiveness of each adhesive of these Examples and Comparative Examples were evaluated as follows: In the following, for each evaluation item, "◯" represents passing, and "Δ" or "×" represents failing. <Initial adhesion> As a substrate 1 for evaluating the adhesive properties of the adhesive of the present invention, a urethane foam (product name) Color Foam EMO (8 cm x 18 cm x thickness t 2.5 cm) manufactured by Inoac Corporation was prepared. Fig. 1 is a front view of the substrate 1.

[0043] Next, the substrate 1 is folded in the center in the longitudinal direction, i.e., along folding line 2 shown by the dashed line in Figure 1, and 12 mm of masking tape is attached to the top and bottom ends of this folding direction. In an environment of 20°C, 70 g / m2 of each composition of the Examples and Comparative Examples is sprayed onto the substrate, and after application, the substrate is folded after the open time described below has elapsed.

[0044] This was evaluated based on the following criteria: A pinch test was conducted on the foams to see whether the foam's rebound could be suppressed after different open times (30 seconds, 1 minute, 3 minutes, and 5 minutes). ○: Open time is within 1 minute △: Open time is over 1 minute and less than 3 minutes ×: Open time exceeds 3 minutes

[0045] <Removability> Each adhesive of the Examples and Comparative Examples was touched with the thumb and index finger, and in this state the thumb and index finger were rubbed together to evaluate the degree of adhesive removal. ○: The film was easily removed by rubbing fingers together ×: It was difficult to remove the film by rubbing the fingers together.

[0046] <High temperature storage> The test pieces were left in an environment at 50°C, and the condition after leaving them for the specified number of days was evaluated according to the following criteria. As mentioned above, the actual usage environment of the present invention is assumed to be 40°C or higher, but in order to evaluate the properties under more severe temperature conditions, the test was conducted in an environment of 50°C. Shelf life 1: Left for 3 days Shelf life 2: Left for 7 days Evaluation of the condition after abandonment ○: No discoloration and no separation or sedimentation △: Color loss and no separation or sedimentation ×: Discoloration and separation and sedimentation occurred

[0047] The evaluation results of each adhesive of the Examples and Comparative Examples are shown in Tables 1 and 2, respectively. [Table 1]

[0048] [Table 2]

[0049] The evaluation results shown in Table 1 indicate that the aqueous urethane foam adhesive of Formulation Example 1 passed all evaluation criteria. All of the properties of initial adhesion, cleanability, and high-temperature storage stability met the objectives of the present invention.

[0050] All of Comparative Examples 1 to 7 satisfied the initial adhesion and washability requirements, but none of them satisfied the desired storage stability requirements. [Explanation of symbols]

[0051] 1 Base material 2. Folding lines

Claims

[Claim 1] The solid content is 40-60%. 35 to 65 parts by weight of a chloroprene latex (a1) having a toluene dissolution transparency of 4 cm or more as defined below, and 85 to 115 parts by weight of a chloroprene latex (a2) having a toluene dissolution transparency of less than 4 cm as defined below, a total of 150 parts by weight of a chloroprene latex mixture (a) obtained by mixing the above; 0.3 to 1.7 parts by weight of a surfactant; 6 to 17 parts by weight of an antioxidant; 8 to 22 parts by weight of styrene-butadiene rubber; Chloroprene latex adhesives, including: Toluene solution transparency: Transparency (expressed in cm) measured in accordance with JIS K 0102:2016 for a solution prepared by dissolving 1 part by weight of a resin film obtained by drying a chloroprene latex resin at room temperature in 10 parts by weight of toluene.

Images