Composition for hot-melt adhesive

Abstract

Provided is a composition which is for a hot-melt adhesive, contains a poly(3-hydroxyalkanoate)-based resin, has a reduced melt viscosity, and has good mechanical properties.　The composition for a hot-melt adhesive contains a poly(3-hydroxyalkanoate)-based resin (A), and a polycaprolactone (B). The poly(3-hydroxyalkanoate)-based resin (A) may be a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer. A laminate can be produced by melting, through heating, the composition for a hot-melt adhesive, applying the molten composition to a first substrate, then bonding a coated surface to a second substrate, and cooling the composition to bond the first substrate and the second substrate.

Description

Hot melt adhesive composition

[0001] The present invention relates to a hot melt adhesive composition.

[0002] Hot melt adhesives are adhesives that are solid at room temperature and contain a thermoplastic resin as their main component, and are used, for example, to seal cardboard boxes, cartons, etc. When using a hot melt adhesive, for example, the adhesive is heated and melted using a hot gun or the like and applied to the bonding surfaces, and then the substrates are bonded together, and the adhesive is then cooled and solidified, thereby bonding the substrates together.

[0003] Known resin materials that are the main components of such hot melt adhesives include ethylene-vinyl acetate (EVA) copolymers, ethylene-acrylate copolymers, polyolefins, polyamides, polyesters, polycarbonates, and synthetic rubbers.

[0004] On the other hand, plastic waste is a burden on the global environment, affecting ecosystems, emitting harmful gases when burned, and contributing to global warming due to the large amount of heat generated by combustion. Therefore, there has been active development of biodegradable plastics as a material that can solve these problems.

[0005] Patent Document 1 discloses a hot melt adhesive that utilizes a biodegradable plastic, specifically a hot melt adhesive whose main component is a polymer that includes a block of lactic acid and a block of aliphatic polyester composed of a diol and a dicarboxylic acid.

[0006] However, although biodegradable plastics such as polylactic acid can be biodegraded in compost, they cannot be expected to biodegrade in a short period of time in the cold ocean. In this context, poly(3-hydroxyalkanoate) resins are attracting attention because they are materials that can biodegrade even in seawater.

[0007] Patent Document 2 discloses the use of a solution of a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer, which is a type of poly(3-hydroxyalkanoate) resin, and an organic solvent as a biodegradable adhesive. However, there has been no report on the use of a poly(3-hydroxyalkanoate) resin in a hot-melt adhesive.

[0008] JP 2021-102775 A International Publication No. 2021 / 153250 A

[0009] The inventors of the present invention have conducted research and found that poly(3-hydroxyalkanoate) resins generally have high melt viscosities, making it difficult to heat-melt them as hot-melt adhesives and apply them to substrates. On the other hand, they have also found that using poly(3-hydroxyalkanoate) resins with relatively low molecular weights reduces the melt viscosity, but also leads to problems such as reduced mechanical properties.

[0010] In view of the above-described current situation, an object of the present invention is to provide a hot melt adhesive composition that contains a poly(3-hydroxyalkanoate) resin, has a reduced melt viscosity, and has good mechanical properties.

[0011] As a result of extensive research, the present inventors have found that by using a poly(3-hydroxyalkanoate) resin in combination with polycaprolactone, a type of biodegradable resin, to form a hot melt adhesive, it is possible to provide a hot melt adhesive composition that has a reduced melt viscosity and good mechanical properties, and have thus completed the present invention.

[0012] That is, the present invention relates to a hot melt adhesive composition containing a poly(3-hydroxyalkanoate) resin (A) and a polycaprolactone (B). The present invention also relates to a method for producing a laminate, which comprises melting the hot melt adhesive composition under heating, applying it to a first substrate, laminating the coated surface to a second substrate, and cooling the composition to bond the first substrate and the second substrate.

[0013] According to the present invention, it is possible to provide a hot melt adhesive composition that contains a poly(3-hydroxyalkanoate) resin, has a reduced melt viscosity, and has good mechanical properties.

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0015] The hot melt adhesive composition according to this embodiment contains at least a poly(3-hydroxyalkanoate) resin (A) and a polycaprolactone (B).

[0016] <Poly(3-hydroxyalkanoate)-based resin (A)> Poly(3-hydroxyalkanoate)-based resin is a general term for polymers containing at least 3-hydroxyalkanoic acid as a monomer unit, and is generally biodegradable. Hereinafter, poly(3-hydroxyalkanoate)-based resin may be abbreviated as P3HA. P3HA is an aliphatic polyester, and preferably a polyester that does not contain an aromatic ring. Only one type of P3HA may be used, or two or more types may be used in combination.

[0017] The P3HA has the formula: [—CHR—CH ２ 3-hydroxyalkanoic acid repeating units represented by the formula: —CO—O— (wherein R is C ｎ H ２ｎ＋１ where n is an integer of 1 to 15) as an essential repeating unit. The P3HA preferably contains 3-hydroxyalkanoic acid repeating units represented by the above formula in an amount of 50 mol % or more, and more preferably 70 mol % or more, of all monomer repeating units (100 mol %).

[0018] The P3HA may be a homopolymer or a copolymer. When the P3HA is a copolymer, it may be a copolymer containing two or more types of repeating units represented by the above formula, or a copolymer containing a repeating unit represented by the above formula and other repeating units. The type of copolymerization is not particularly limited, and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc., but random copolymerization is preferred because it is easily available.

[0019] Specific examples of P3HA include poly(3-hydroxybutyrate) (abbreviation: P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), poly(3-hydroxybutyrate-co Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH), etc. Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because of their ease of industrial production.

[0020] By changing the composition ratio of the repeating units in P3HA, the melting point or crystallinity of the PHA can be changed, and as a result, physical properties such as Young's modulus and heat resistance can be changed. In addition, it is possible to impart physical properties between those of polypropylene and polyethylene. From the viewpoints of ease of industrial production and being a physically useful plastic, P3HB3HH, which is a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoic acid, is particularly preferred.

[0021] P3HA can be produced by microorganisms. Such microbially produced P3HA is usually P3HA composed only of D-form (R-form) hydroxyalkanoic acid repeating units. Among microbially produced P3HAs, P3HB and P3HB3HH are preferred, with P3HB3HH being more preferred, due to ease of industrial production.

[0022] When P3HA contains 3-hydroxybutyrate (3HB) units, from the viewpoint of the balance between flexibility or workability and initial fixability, the average content ratio of repeating units in P3HA is preferably 3-hydroxybutyrate units / other hydroxyalkanoate units (3-hydroxyhexanoate units when P3HA is P3HB3HH) from 97 / 3 to 75 / 25 (mol / mol), more preferably 95 / 5 to 80 / 20 (mol / mol), and particularly preferably 95 / 5 to 85 / 15 (mol / mol).

[0023] When the average content of the other hydroxyalkanoate units in P3HA is 3 mol% or more, the flexibility of P3HA can be improved, and the melting point can be lowered, improving the workability when melting and applying a hot melt adhesive composition.Furthermore, when the average content of the other hydroxyalkanoate units in P3HA is 25 mol% or less, a moderate crystallization rate can be achieved, and the initial fixation can be improved when melting and applying a hot melt adhesive composition and bonding it to another substrate.

[0024] Two or more types of P3HA having different average repeating unit content ratios can be used in combination. In this case, the numerical range of the average content ratio refers to the average repeating unit content ratio contained in the entire mixture of two or more P3HA types contained in the hot melt adhesive composition. The average repeating unit content ratio of P3HA can be measured by hydrolysis or alcohol esterification to the monomer unit and gas chromatography or the like (see, for example, WO 2014 / 020838).

[0025] The molecular weight of P3HA is not particularly limited, but from the viewpoint of the balance between adhesive strength and workability during melt application, the weight average molecular weight is preferably 10,000 to 1,500,000, more preferably 100,000 to 1,000,000, and even more preferably 150,000 to 800,000. When the weight average molecular weight is 10,000 or more, the strength of the adhesive layer is good and sufficient adhesive strength can be achieved. On the other hand, when it is 1,500,000 or less, the melt viscosity is reduced, and workability can be improved when the hot melt adhesive composition is melted and applied.

[0026] As P3HA, two or more types of P3HA having different weight-average molecular weights may be used in combination. In particular, since the balance between reduced melt viscosity and good mechanical properties is particularly excellent, a P3HA having a relatively high molecular weight and a P3HA having a relatively low molecular weight may be used in combination. The weight-average molecular weights of these two types of P3HA can be appropriately selected from the range of weight-average molecular weights described above.

[0027] The weight average molecular weight can be measured using gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) with a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column, chloroform as a mobile phase, and the weight average molecular weight can be calculated as a polystyrene-equivalent molecular weight. As the column for the GPC, a column appropriate for measuring the molecular weight may be used.

[0028] The microorganism that produces P3HA is not particularly limited as long as it has the ability to produce P3HA. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925, and other naturally occurring microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus are known. In these microorganisms, P3HB accumulates intracellularly.

[0029] Known examples of bacteria that produce copolymers of 3HB with other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)), into which genes encoding P3HA synthases have been introduced, is preferred. Microbial cells obtained by culturing such microorganisms under appropriate conditions and allowing P3HA to accumulate within the cells are used. In addition to the above, genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced may be used depending on the P3HA to be produced, or culture conditions, including the type of substrate, may be optimized.

[0030] <Polycaprolactone (B)> Polycaprolactone is a compound represented by the formula: [-(CH ２ ) ５ -CO-O-]. Hereinafter, polycaprolactone may be abbreviated as PCL. PCL can usually be produced by ring-opening polymerization of ε-caprolactone using a cationic or anionic initiator. An organometallic catalyst may be used to promote the polymerization. However, PCL obtained by other production methods can also be used. Furthermore, the end-capping structure is not particularly limited. PCL generally has a melting point of 50 to 65°C, a crystallization temperature of 10 to 30°C, and a glass transition point of -50 to -60°C, but is not limited thereto.

[0031] The molecular weight of PCL is not particularly limited, but from the viewpoint of the balance between adhesive strength and workability during melt application, the weight-average molecular weight is preferably 1,000 to 500,000, more preferably 5,000 to 400,000, even more preferably 10,000 to 300,000, and particularly preferably 20,000 to 250,000. When the weight-average molecular weight is 1,000 or more, the strength of the adhesive layer is good and sufficient adhesive strength can be achieved. On the other hand, when it is 500,000 or less, the melt viscosity is reduced, and workability can be improved when the hot melt adhesive composition is melted and applied.

[0032] In particular, from the viewpoint of improving mechanical properties such as strength and elongation, the weight-average molecular weight of PCL is preferably 100,000 or more, and more preferably 120,000 or more. On the other hand, from the viewpoint of further reducing the melt viscosity, the weight-average molecular weight of PCL is preferably less than 100,000, more preferably 90,000 or less, and even more preferably 70,000 or less.

[0033] As the PCL, two or more types of PCL having different weight-average molecular weights may be used in combination. In particular, a preferred embodiment is one in which a first PCL having a relatively high molecular weight and a second PCL having a relatively low molecular weight are used in combination, as this provides a particularly excellent balance between reduced melt viscosity and good mechanical properties.

[0034] In this embodiment, the weight average molecular weight of the first PCL is preferably 100,000 or more, more preferably 120,000 or more, and the weight average molecular weight of the second PCL is preferably 70,000 or less, more preferably 50,000 or less, and even more preferably 40,000 or less.

[0035] The ratio of the first PCL having a relatively high molecular weight to the second PCL having a relatively low molecular weight is not particularly limited, but the weight ratio of the first PCL / second PCL is preferably 95 / 5 to 40 / 60, more preferably 90 / 10 to 50 / 50, and even more preferably 85 / 15 to 60 / 40. When both PCLs are used in combination within this range, it is possible to achieve a high level of both improved mechanical properties by the first PCL and reduced melt viscosity by the second PCL.

[0036] The weight-average molecular weight of PCL can be measured by the same method as in the case of the weight-average molecular weight of P3HA described above.

[0037] In the hot melt adhesive composition, the content ratio of the poly(3-hydroxyalkanoate) resin (A) to the polycaprolactone (B) can be set as appropriate, but a weight ratio of component (A) / component (B) of 95 / 5 to 5 / 95 is preferred. Within this range, a hot melt adhesive composition can be provided that utilizes a poly(3-hydroxyalkanoate) resin that is seawater degradable, while exhibiting reduced melt viscosity and excellent mechanical properties. The weight ratio is more preferably 90 / 10 to 10 / 90, even more preferably 80 / 20 to 20 / 80, and particularly preferably 70 / 30 to 30 / 70. It may also be 95 / 5 to 50 / 50, or 50 / 50 to 5 / 95. From the viewpoint of further reducing the melt viscosity, a ratio of 50 / 50 to 5 / 95 is preferred.

[0038] <Glycerin fatty acid ester (C)> The hot melt adhesive composition according to this embodiment may further contain a glycerin fatty acid ester (C). By blending the glycerin fatty acid ester (C), it is possible to significantly reduce the melt viscosity while maintaining a certain degree of mechanical properties.

[0039] As the glycerin fatty acid ester, any of glycerin monoesters, diesters, and triesters can be used, but from the viewpoint of compatibility with the poly(3-hydroxyalkanoate) resin (A) and polycaprolactone (B), glycerin triesters are preferred. Among glycerin triesters, glycerin diacetomonoesters are particularly preferred. Specific examples of glycerin diacetomonoesters include glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin diacetomonostearate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate. Of these, glycerin diacetomonolaurate is preferred. Commercially available products of the modified glycerin compounds include Riken Vitamin Co., Ltd.'s "BIOCIZER" and "Rikemal" (registered trademark) PL series.

[0040] In the hot melt adhesive composition, the content of the glycerin fatty acid ester (C) is preferably 0 to 50 parts by weight per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polycaprolactone (B). The lower limit is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 5 parts by weight or more. The upper limit is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less.

[0041] <Other Components> The hot melt adhesive composition may contain only the poly(3-hydroxyalkanoate) resin (A) and polycaprolactone (B) as resin components, or may further contain other resins. Such other resins are preferably biodegradable resins, and examples thereof include aliphatic polyester resins such as polybutylene succinate and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate.

[0042] The content of these other resins may be about 0 to 30 parts by weight, preferably 0 to 10 parts by weight, more preferably 0 to 5 parts by weight, and particularly preferably 0 to 1 part by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polycaprolactone (B).

[0043] The hot melt adhesive composition may further contain a plasticizer other than the glycerin fatty acid ester (C). Examples of such plasticizers include, but are not limited to, dibasic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoate ester compounds, citrate ester compounds, and isosorbide ester compounds.

[0044] Examples of the dibasic acid ester compounds include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl succinate, and mixed-group dibasic acid ester compounds.

[0045] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0046] Examples of the polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0047] The content of the plasticizer other than the glycerin fatty acid ester (C) may be about 0 to 30 parts by weight, preferably 0 to 10 parts by weight, more preferably 0 to 5 parts by weight, and particularly preferably 0 to 1 part by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polycaprolactone (B).

[0048] The hot melt adhesive composition may contain additives commonly used in the adhesives field. Examples of such additives include inorganic fillers such as talc, calcium carbonate, mica, silica, titanium oxide, and alumina; organic fillers such as rice husk, wood flour, and recycled paper such as newspaper; various starches and cellulose; colorants such as pigments and dyes; odor absorbers such as activated carbon and zeolite; fragrances such as vanillin and dextrin; antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, sliding property improvers, tackifiers, fillers, and chemicals. The additives may be used alone or in combination. The solids concentration of the additives can be appropriately set depending on the intended use.

[0049] <Hot melt adhesive composition> The hot melt adhesive composition according to this embodiment is solid or semi-solid at room temperature (usually about 15 to 30°C). At room temperature, it does not exhibit fluidity suitable for application, but when heated to an appropriate temperature and melted, it exhibits fluidity suitable for application.

[0050] The hot melt adhesive composition is substantially free of volatile organic solvents or water. Specifically, the total amount of organic solvents and water in the hot melt adhesive composition is preferably 10% by weight or less, more preferably 1% by weight or less, and even more preferably 0.1% by weight or less.

[0051] The hot melt adhesive composition may be used as a hot melt adhesive as it is, or may be used as a hot melt adhesive after being subjected to processing such as the addition of appropriate additives or adjustment of the shape.

[0052] The shape of the hot melt adhesive composition is not particularly limited, but any shape commonly used for hot melt adhesives can be adopted, and specific examples include a stick (rod), pellet (granule), sheet, or film shape.

[0053] The hot melt adhesive composition has a relatively low viscosity when heated and melted, i.e., a relatively low melt viscosity, and therefore can be easily applied to a substrate by melting the hot melt adhesive composition.

[0054] As an indicator of such a relatively low melt viscosity, the hot melt adhesive composition was measured using a capillograph at a shear rate of 1.2 × 10 ２ s －１ and the melt viscosity measured at a temperature of 150°C is preferably 2,900 Pa·s or less, more preferably 2,000 Pa·s or less, even more preferably 1,500 Pa·s or less, and particularly preferably 1,000 Pa·s or less.

[0055] The hot melt adhesive composition can be used to bond two substrates after being heated and melted. Specifically, the hot melt adhesive composition is heated to melt it and applied to a first substrate, and then the coated surface is attached to a second substrate, and the composition is cooled and solidified, thereby bonding the first substrate and the second substrate. A glue gun or a hot gun can be used to heat and apply the hot melt adhesive composition to the first substrate.

[0056] Alternatively, the first substrate and the second substrate can be bonded together by placing the hot melt adhesive composition on the first substrate and the second substrate, heating the composition to melt the composition, and then cooling the composition.

[0057] The heating temperature when melting the hot melt adhesive composition can be appropriately set taking into consideration the melting point of the hot melt adhesive composition, and may be, for example, within the range of about 100 to 180°C.

[0058] The type of substrate on which the hot melt adhesive composition can be used is not particularly limited, but since the hot melt adhesive composition is biodegradable, it is preferable that the substrate also be biodegradable. The shape of the substrate is not particularly limited.

[0059] The biodegradable substrate is not particularly limited, but examples thereof include paper (mainly composed of cellulose), cellophane, cellulose ester, polyvinyl alcohol, polyamino acid, polyglycolic acid, pullulan, biodegradable polyester, etc. Furthermore, these substrates can also be used with inorganic materials such as aluminum and silica vapor-deposited. Among these, paper and biodegradable polyester are preferred because of their excellent heat resistance and biodegradability.

[0060] The type of paper is not particularly limited, and examples include cup base paper, one-side glazed paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard.

[0061] The biodegradable polyester that can constitute the substrate is not particularly limited, and examples thereof include aliphatic polyester resins such as polybutylene succinate (PBS)-based resins, polycaprolactone-based resins, and polyhydroxyalkanoate-based resins, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate (PBAT)-based resins, polybutylene sebatate terephthalate-based resins, and polybutylene succinate terephthalate-based resins.

[0062] The substrate may contain, as necessary, a water-resistant agent, a water-repellent agent, an inorganic substance, or the like, or may be subjected to a surface treatment such as an oxygen barrier layer coating or a water vapor barrier coating.

[0063] The use of the hot melt adhesive composition is not particularly limited, and the composition can be used for various bonding applications. Specific examples include sealing cardboard boxes, sealing cartons (paper boxes), and assembling sanitary materials (for example, disposable diapers).

[0064] The following items list preferred embodiments of the present disclosure, but the present invention is not limited to them. [Item 1] A hot melt adhesive composition containing a poly(3-hydroxyalkanoate)-based resin (A) and polycaprolactone (B). [Item 2] The hot melt adhesive composition according to Item 1, wherein the poly(3-hydroxyalkanoate)-based resin (A) is a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer. [Item 3] The hot melt adhesive composition according to Item 2, wherein the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer has an average content of 3-hydroxyhexanoate units of 3 to 25 mol %. [Item 4] The hot melt adhesive composition is a hot melt adhesive composition having a shear rate of 1.2 x 10 ２ s －１and a melt viscosity measured at a temperature of 150°C of 2,900 Pa s or less. [Item 5] The hot melt adhesive composition according to any one of Items 1 to 4, wherein the poly(3-hydroxyalkanoate) resin (A) has a weight average molecular weight of 100,000 to 1,000,000. [Item 6] The hot melt adhesive composition according to any one of Items 1 to 5, wherein the polycaprolactone (B) has a weight average molecular weight of 20,000 to 250,000. [Item 7] The hot melt adhesive composition according to any one of Items 1 to 6, wherein the polycaprolactone (B) comprises two or more types of polycaprolactone having mutually different weight average molecular weights. [Item 8] The hot melt adhesive composition according to any one of Items 1 to 7, wherein the weight ratio of the poly(3-hydroxyalkanoate) resin (A) / polycaprolactone (B) is 95 / 5 to 5 / 95. [Item 9] The hot melt adhesive composition according to any one of Items 1 to 8, further containing a glycerin fatty acid ester (C). [Item 10] The hot melt adhesive composition according to Item 9, wherein the glycerin fatty acid ester (C) is glycerin diacetomonolaurate. [Item 11] The hot melt adhesive composition according to Item 9 or 10, wherein the content of the glycerin fatty acid ester (C) is 50 parts by weight or less per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polycaprolactone (B). [Item 12] A method for producing a laminate, comprising melting the hot melt adhesive composition according to any one of Items 1 to 11 under heating, applying it to a first substrate, laminating the coated surface to a second substrate, and cooling the composition to bond the first substrate and the second substrate.

[0065] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0066] In the examples and comparative examples, the following raw materials were used. [Poly(3-hydroxyalkanoate) resins (A) used] Poly(3-hydroxyalkanoate) resin (A-1): average content ratio 3HB / 3HH = 89 / 11 (mol% / mol%), weight average molecular weight 600,000 g / mol Poly(3-hydroxyalkanoate) resin (A-2): average content ratio 3HB / 3HH = 89 / 11 (mol% / mol%), weight average molecular weight 200,000 g / mol

[0067] [Polycaprolactone (B)] (B-1): Poly-ε-caprolactone: manufactured by Fujifilm Wako Pure Chemical Industries, weight average molecular weight 28,500 (B-2): Capa 6250: manufactured by Ingevity, weight average molecular weight 66,200 (B-3): Capa 6400: manufactured by Ingevity, weight average molecular weight 80,900 (B-4): Capa 6500: manufactured by Ingevity, weight average molecular weight 138,800 (B-5): Capa 6800: manufactured by Ingevity, weight average molecular weight 232,500

[0068] Glycerin fatty acid ester (C): BIOCIZER manufactured by Riken Vitamin

[0069] [Method for measuring weight-average molecular weight] The weight-average molecular weight of each resin was determined as a polystyrene-equivalent molecular weight by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase.

[0070] (Examples 1 to 42) Poly(3-hydroxyalkanoate) resin (A) and polycaprolactone (B) were charged into a kneading and extrudability tester (Labo Plastomill, manufactured by Toyo Seiki Seisakusho) in a weight ratio shown in each table so that the total amount was 40 g, and kneading was performed for 5 to 10 minutes at 150° C. In Examples 33 to 42, the total amount of (A) + (B) (40 g) was 100 parts by weight, and glycerin fatty acid ester (C) in the number of parts by weight shown in the table was additionally charged into the kneading and extrudability tester, and kneading was performed in the same manner.

[0071] Comparative Examples 1 and 2 According to the description in the table, only the poly(3-hydroxyalkanoate) resin (A) was used.

[0072] [Melt Viscosity] The melt viscosity of the kneaded product obtained in each Example, or the melt viscosity of the poly(3-hydroxyalkanoate) resin (A) in Comparative Examples 1 and 2, was measured by a capillograph. The measurement temperature was 150°C. Each table shows the melt viscosity at an extrusion rate of 10 mm / min (shear rate of 1.2 × 10 ２ s －１ The melt viscosity (Pa·s) at 100°C was recorded.

[0073] [Tensile Test] The kneaded product obtained in each Example, or the poly(3-hydroxyalkanoate) resin (A) in Comparative Examples 1 and 2, was press-molded at 160°C to obtain a sheet having a thickness of 100 μm. A No. 3 dumbbell-shaped test piece was cut out from the obtained sheet and used as a sample for the tensile test. The tensile test was carried out using an AG-2000A manufactured by Shimadzu Corporation, with a measurement temperature of 23°C and a tensile speed of 50 mm / min. Each table shows the strength at break (MPa) and elongation at break (%).

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] Table 1 shows the results of Comparative Examples 1 and 2, in which melt viscosity and tensile tests were performed on poly(3-hydroxyalkanoate) resin (A) alone. Comparative Example 1 had relatively good mechanical properties, but its melt viscosity was high and it was not suitable for use as a hot melt adhesive. On the other hand, Comparative Example 2, in which a poly(3-hydroxyalkanoate) resin (A) with a relatively low molecular weight was used, showed a lower melt viscosity than Comparative Example 1, but the elongation at break was significantly reduced.

[0081] In each of the Examples in Tables 2 to 6, melt viscosity and tensile tests were carried out on kneaded materials prepared by using poly(3-hydroxyalkanoate) resin (A) in combination with polycaprolactone (B). Each Example had a lower melt viscosity than Comparative Example 1, making it possible to use the material as a hot melt adhesive. Furthermore, the elongation at break was greater than that of Comparative Example 2, and the mechanical properties were excellent.

Claims

1. A hot melt adhesive composition comprising a poly(3-hydroxyalkanoate)-based resin (A) and a polycaprolactone (B), wherein the poly(3-hydroxyalkanoate)-based resin (A) is a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer.

2. 2. The hot melt adhesive composition according to claim 1, wherein the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer has an average content of 3 to 25 mol % of 3-hydroxyhexanoate units.

3. The hot melt adhesive composition was applied at a shear rate of 1.2 × 10 ２ s －１ 3. The hot melt adhesive composition according to claim 1, wherein the melt viscosity measured at a temperature of 150°C is 2,900 Pa·s or less.

4. 3. The hot melt adhesive composition according to claim 1, wherein the poly(3-hydroxyalkanoate) resin (A) has a weight average molecular weight of 100,000 to 1,000,000.

5. The hot melt adhesive composition according to claim 1 or 2, wherein the polycaprolactone (B) has a weight average molecular weight of 20,000 to 250,000.

6. The hot melt adhesive composition according to claim 1 or 2, wherein the polycaprolactone (B) comprises two or more types of polycaprolactone having different weight average molecular weights.

7. 3. The hot melt adhesive composition according to claim 1, wherein the weight ratio of the poly(3-hydroxyalkanoate) resin (A) to the polycaprolactone (B) is 95 / 5 to 5 / 95.

8. The hot melt adhesive composition according to claim 1 or 2, further comprising a glycerin fatty acid ester (C).

9. The hot melt adhesive composition according to claim 8, wherein the glycerin fatty acid ester (C) is glycerin diacetomonolaurate.

10. 9. The hot melt adhesive composition according to claim 8, wherein the content of the glycerin fatty acid ester (C) is 50 parts by weight or less per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polycaprolactone (B).

11. A method for manufacturing a laminate, comprising:

3. A method for producing a laminate, comprising: melting the hot melt adhesive composition according to claim 1 under heating; applying the composition to a first substrate; bonding the coated surface to a second substrate; and cooling the composition to bond the first substrate and the second substrate.