Photocurable adhesive composition

Abstract

To provide a biomass photocurable adhesive composition that uses environmentally friendly raw material derived from plants, and also has excellent adhesive strength to glass.SOLUTION: A photocurable adhesive composition includes: urethane methacrylate synthesized from plant-derived biomass polyol, alicyclic polyisocyanate and hydroxylated methacrylate; a methacryloylate compound having a polar group; aliphatic methacrylate; and a photopolymerization initiator, with the urethane methacrylate having a weight average molecular weight of 1000-6000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a photocurable adhesive composition made from plant-derived components. [Background technology]

[0002] In recent years, due to concerns about the depletion of petroleum resources and the problem of increasing carbon dioxide in the atmosphere that causes global warming and climate change, biomass resources, which do not rely on petroleum resources as raw materials and do not increase carbon dioxide when burned, thus achieving carbon neutrality, have attracted considerable attention. As a result, various biomass-type adhesives produced from plant-derived biomass resources have been developed for use in adhesives.

[0003] For example, an adhesive sheet has been proposed that contains a polyester obtained by condensation polymerization of dimer acid, a plant-derived dicarboxylic acid, and dimer ol, a plant-derived diol, a radiation-curable resin, and an adhesive layer that has been crosslinked with a crosslinking agent (Patent Document 1).

[0004] On the other hand, in the field of adhesives other than adhesives, for example, a two-component curing adhesive composition has been proposed that uses an aromatic polyester urethane polyol of a specific component containing plant-derived components as the main component and a polyfunctional isocyanate compound as the curing agent (Patent Document 2). However, many of these raw materials are still composed of petroleum-derived materials. For this reason, there has been a growing demand for adhesives with a high biomass content, and in particular, there has been a need for a highly transparent biomass-type adhesive that is photocurable, capable of curing in a short time, and has excellent adhesion to glass. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6097132 [Patent Document 2] Patent No. 5942032 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a highly transparent, light-curing adhesive composition that uses plant-derived raw materials that are environmentally friendly, allows for short curing times, and has excellent adhesion to glass. [Means for solving the problem]

[0007] To solve the above problems, the invention of claim 1 is a plant-derived Polypropanediol A urethane (meth)acrylate (A) synthesized from (a1), an alicyclic polyisocyanate (a2), and a (meth)acrylate (a3) ​​having a hydroxyl group, and a compound (B) containing a polar group (meth)acryloyl group, Alkyl chain and / or alicyclic The (meth)acrylate (C) and the photopolymerization initiator (D) are included, and the weight-average molecular weight of (A) is 1000 to 6000. The proportion of (A) relative to the total solid content is 10-70% by weight, the proportion of (B) is 10-60% by weight, and the proportion of (C) is 3-55% by weight. The present invention provides a photocurable adhesive composition characterized by the following:

[0008] Furthermore, the invention of claim 2 is as described above. (C) contains an alicyclic (meth)acrylate The present invention provides a photocurable adhesive composition according to claim 1.

[0009] Furthermore, the invention of claim 3 is as described above. (C) represents the number of carbon atoms from C8 to C16. The present invention provides a photocurable adhesive composition according to either claim 1 or 2, characterized in that it is such.

[0010] Furthermore, the invention described in claim 4 provides a photocurable adhesive composition according to any one of claims 1 to 3, characterized in that (B) comprises a (meth)acrylate having a hydroxyl group. [Effects of the Invention]

[0011] The composition of the present invention uses plant-derived raw materials that take environmental issues into consideration, has good curability against light such as ultraviolet rays, and also has excellent transparency and adhesion to glass, making it useful as a biomass-type photocurable adhesive for optical applications. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below.

[0013] The composition of the present invention comprises a urethane (meth)acrylate (A) synthesized from a plant-derived biomass polyol, a monofunctional (meth)acryloyl group-containing compound having a polar group (B), an aliphatic (meth)acrylate (C), and a photopolymerization initiator (D). In this specification, (meth)acrylate encompasses both acrylate and methacrylate.

[0014] The urethane (meth)acrylate (hereinafter referred to as Ureac) (A) used in the present invention is a base oligomer constituting the adhesive composition, and is synthesized from a plant-derived biomass polyol (a1), an alicyclic polyisocyanate (a2), and a (meth)acrylate (a3) ​​having hydroxyl groups. The number of functional groups of (A) is preferably 4 or less, and more preferably 2. If there are 5 or more functional groups, a network-like polymer structure is formed, which can become too rigid, potentially reducing the adsorption to glass surfaces and conformability to curved surfaces.

[0015] The above (a1) is a component obtained by polymerizing a plant-derived short-chain diol, and examples include polymers of ethylene glycol, propylene glycol, 1,3-propanediol, and 1,4-butanediol, which can be used alone or in combination of two or more. Among these, polypropanediol, a polymer of 1,3-propanediol, is preferred due to its high reactivity, low viscosity, and good adhesion to glass. Polypropanediol can be obtained, for example, by enzymatically decomposing plant resources such as corn into glucose, converting it to biopropanediol using microorganisms, and then polymerizing it.

[0016] The above (a2) can impart high weather resistance and rigidity to the cured product of (A). For example, isophorone diisocyanate (hereinafter referred to as IPDI), hydrogenated diphenylmethane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, hydrogenated xylylene diisocyanate, methylcyclohexylene diisocyanate, IPDI isocyanurate, etc. can be mentioned, and they can be used alone or in combination of two or more. Among these, IPDI with relatively good reactivity and easy availability is preferred.

[0017] The above (a3) preferably has a functionality of 2 or less in order to make the functional group of (A) 4 or less. For example, monofunctional (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and difunctional (meth)acrylates such as glycerin di(meth)acrylate can be mentioned. Among these, C2-C4 monofunctional (meth)acrylates are preferred in terms of adhesive physical properties, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are more preferred.

[0018] There is no particular limitation on the synthesis method of the above (A), and known methods can be used. The blending ratio (molar ratio) of (a1) and (a2) is preferably such that the hydroxyl group of (a1): the isocyanate group of (a2) = 0.7:1 to 1:1, and more preferably 0.8:1 to 1:1. It is preferable to use a catalyst for the above reaction. For example, tin-based catalysts such as dibutyltin dilaurate and metal alkoxide-based catalysts such as cobalt naphthenate can be mentioned. The reaction may be carried out without a solvent, but organic solvents having no functional group reactive with the isocyanate group, such as esters such as ethyl acetate and butyl acetate, and ketones such as methyl ethyl ketone and isobutyl ketone can be used. The reaction temperature can be set appropriately, but 40-110°C is preferred, and 50-90°C is more preferred. The reaction time can also be set appropriately, but 2-14 hours is preferred, and 4-10 hours is more preferred.

[0019] The weight-average molecular weight (hereinafter referred to as Mw) of (A) is 1,000 to 6,000, preferably 2,000 to 5,000, and more preferably 2,500 to 4,500. Below 1,000, the cohesive force of the cured film is low and the peel strength decreases, and above 6,000, the adhesion to glass tends to weaken. Mw was measured and calculated using gel permeation chromatography with a column packed with styrenedivinylbenzene substrate and tetrahydrofuran eluent, to obtain the molecular weight on a standard polystyrene basis.

[0020] The amount of (A) added to the total solid content is preferably 10 to 70% by weight, more preferably 15 to 65% by weight, and particularly preferably 18 to 60% by weight. A concentration of 10% by weight or more ensures sufficient cohesive force and film strength, while a concentration of 70% by weight or less makes it easier to control the viscosity to a level suitable for workability.

[0021] The polar group-containing (meth)acryloyl group compound (B) used in the present invention is added in combination with (A) to improve adhesion to glass. Examples include (meth)acrylates having hydroxyl groups and amino groups, and acrylamides, which can be used alone or in combination of two or more. Furthermore, monofunctional compounds are preferable in that they do not increase the molecular weight of the cured product too much. Examples include hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyhexyl (meth)acrylate; amino group-containing (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylamide and N,N-dimethylaminopropyl (meth)acrylamide; and acrylamides such as N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and acryloyl morpholine. Among these, 4-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, and acryloyl morpholine are preferred in that they provide good adhesion.

[0022] The amount of (B) added relative to the total solid content is preferably 10 to 60% by weight, more preferably 12 to 55% by weight, and particularly preferably 15 to 50% by weight. Sufficient glass adhesion can be ensured by keeping it within this range.

[0023] The aliphatic (meth)acrylate (C) used in this invention is added to improve reactivity and to further stabilize adhesion to glass. It is preferable that the carbon number be between C8 and C16, and that it be monofunctional, in order to avoid excessively increasing the storage modulus of the cured product. Examples include linear (meth)acrylates such as octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and tetradecyl acrylate, as well as alicyclic (meth)acrylates such as dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. These can be used individually or in combination of two or more. Among these, isobornyl acrylate is preferred for its moderate rigidity, while octyl acrylate and lauryl acrylate are preferred for their good adhesion to glass.

[0024] The amount of (C) added relative to the total solid content is preferably 3 to 55% by weight, more preferably 5 to 50% by weight, and particularly preferably 8 to 48% by weight. By setting it within this range, it is possible to further stabilize the adhesion to the glass.

[0025] The photopolymerization initiator (D) used in this invention generates radicals upon irradiation with ultraviolet light or electron beams, and these radicals trigger the polymerization reaction. General-purpose photopolymerization initiators such as benzyl ketal, acetophenone, and phosphine oxide can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, examples include 2,2-dimethoxy-1,2-diphenylethane-1-one as a benzyl ketal, 1-hydroxycyclohexylphenyl ketone and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one as α-hydroxyacetophenones, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one as an α-aminoacetophenone, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide as acylphosphine oxides, which can be used individually or in combination of two or more. Among these, it is preferable to include an acylphosphine oxide that exhibits excellent internal curing properties.

[0026] The amount of (D) is preferably 0.1 to 5.0 parts by weight, and more preferably 0.2 to 2.0 parts by weight, per 100 parts by weight of the radical polymerizable component. By blending within this range, the composition can be cured efficiently. A commercially available acyl phosphine oxide product is OmniradTPO H (trade name: manufactured by IGM Resins).

[0027] Furthermore, the adhesive composition of the present invention may contain additives such as antioxidants, polymerization inhibitors, photosensitizers, flame retardants, leveling agents, fillers, silane coupling agents, colorants, organic fine particles, and inorganic fine particles, as needed, within limits that do not impair its performance.

[0028] The aforementioned antioxidant, when incorporated, can prevent deterioration of the film's physical properties after curing. Examples of antioxidants include phenol-based, phosphorus-based, phenol-phosphorus-based, and sulfur-based types, which can be used individually or in combination of two or more. The amount of antioxidant incorporated is preferably 5% by weight or less, and more preferably 2% by weight or less, relative to the total solid content. A commercially available example is SumiLizer GP (product name: manufactured by Sumitomo Chemical Co., Ltd., phenol-phosphorus-based).

[0029] The polymerization inhibitor, when incorporated, can prevent thickening and improve storage stability. Examples of antioxidants include pyrocatechol, hydroquinone derivatives, and dibutylhydroxytoluene (hereinafter referred to as BHT), which can be used alone or in combination of two or more. The amount of polymerization inhibitor is preferably 5% by weight or less, and more preferably 3% by weight or less, relative to the total solids.

[0030] The adhesive composition of the present invention can be used as a protective film in the production process of image display devices such as touch panels and flat panel displays by applying it to a plastic film. Various known plastic films can be used as the base material, such as polyester film, polyethylene film, polypropylene film, cellophane, diacetylcellulose film, triacetylcellulose film, acetylcellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, polyimide film, fluororesin film, nylon film, acrylic film, and cycloolefin (co)polymer film. The base material plastic film may be a single layer or a laminate of two or more layers. Among these, polyester-based PET film is preferred due to its heat resistance, dimensional stability, light transmittance, and availability.

[0031] The method of applying the adhesive composition of the present invention to a plastic film is not particularly limited, and known methods such as roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, and gravure coating can be used. The coating thickness is arbitrary, for example, 5 to 300 μm can be exemplified, but 20 to 100 μm is preferred in terms of stable fixing of the adherend and suppression of adhesive residue. Known light sources such as high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, LED lamps, and electrodeless lamps can be used as light sources for curing, and the integrated light intensity is for example, 50 to 5,000 mJ / cm². 2 The adhesive composition is cured by irradiation.

[0032] The present invention will be described in detail below based on examples and comparative examples, but these are merely examples and the invention is not limited to them. Unless otherwise stated, measurements were taken under conditions of 25°C and 65% relative humidity. The amounts of ingredients are given in parts by weight.

[0033] Preparation of Ureac 1 In a four-necked flask equipped with a thermometer, stirrer, dropping funnel, and condenser with drying tube, 820 parts by weight of IPDI (37.5% NCO group) and 1550 parts by weight of plant-derived biomass polypropanediol (number average molecular weight 500) were charged. A catalyst was added, the temperature was raised to 60°C, and the mixture was reacted for 4 hours to obtain a urethane prepolymer having isocyanate groups at both ends. Next, 130 parts by weight of 2-HEA was added, the temperature was raised to 70°C, and the mixture was reacted for 2 hours. Infrared absorption analysis confirmed the disappearance of the isocyanate groups, yielding Ureac 1 (skeleton: HEA-IPDI-polypropanediol-IPDI-HEA) with a Mw. of 3,500.

[0034] Following conventional methods, the following Ureac 2-5 was prepared. Ureac 2 (Skeleton: HEA-IPDI-Polypropanediol) ※ -IPDI-HEA), Mw7,000 Ureac 3 (Skeleton: HEA-IPDI-Polypropanediol) ※ -IPDI-HEA), Mw10,000 Ureac 4 (Skeleton: HEA-IPDI-PPG) ※ -IPDI-HEA), Mw15,000 Ureac 5 (Skeleton: HEA-IPDI-PTMG) ※ -IPDI-HEA), Mw5,000 *Polypropanediol: Biomass, PPG: Petroleum-derived polypropylene glycol, PTMG: Petroleum-derived polytetramethylene glycol

[0035] Examples 1-7 Ureac 1 as (A), 4-HBA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate), HOP-A (trade name: manufactured by Kyoeisha Chemical Co., Ltd., 2-hydroxypropyl acrylate), and ACMO (trade name: manufactured by KJ Chemicals Co., Ltd., acryloyl morpholine) as (B), IBXA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., isobornyl acrylate), NOAA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., n-octyl acrylate), and LA (trade name: manufactured by Kyoeisha Chemical Co., Ltd., lauryl acrylate) as (C), OmniradTPO H (trade name: manufactured by IGM Resins, acyl phosphine oxide type) as (D), and BHT (dibutylhydroxytoluene) and SumilizerGP (trade name: manufactured by Sumitomo Chemical Co., Ltd., phenol phosphorus type) as additives were stirred until uniformly dissolved in the formulations shown in Table 1 to prepare the photocurable adhesive compositions of Examples 1 to 7.

[0036] Comparative Examples 1-5 In addition to the materials used in the examples, Ureac 2-5 was added as a binder and stirred until uniformly dissolved according to the formulations shown in Table 1 to prepare the photocurable adhesive compositions of Comparative Examples 1-5.

[0037] Table 1 JPEG0007851142000001.jpg80135

[0038] The evaluation method was as follows:

[0039] Preparation of evaluation glass plates On a plate glass S1126 with a thickness of 1 mm (product name: manufactured by Matsunami Glass Industry Co., Ltd.), a photocurable adhesive composition was applied so that the film thickness after curing would be 30 μm. Using an electrodeless UV irradiation device F300S / LC-6B manufactured by Heraeus, with a D valve and an illuminance of 100 mW / cm 2 , and a cumulative light quantity of 2,000 mJ / cm 2 , it was cured under these conditions to prepare an evaluation plate glass.

[0040] Adhesive strength: On a plate glass S1126 with a thickness of 1 mm (product name: manufactured by Matsunami Glass Industry Co., Ltd.), a photocurable adhesive composition was applied so that the film thickness after curing would be 30 μm. Cosmo Shine A4300 (product name: manufactured by Toyobo Co., Ltd., 50-μm-thick PET film) cut to a width of 25 mm × 150 mm was overlaid, and using an electrodeless UV irradiation device F300S / LC-6B manufactured by Heraeus, with a D valve and an illuminance of 100 mW / cm 2 , and a cumulative light quantity of 2,000 mJ / cm 2 , the cured product was used as a test piece. Using a tensile testing machine TGI-1kN manufactured by Minebea, at a crosshead speed of 300 mm / min., the peel strength at 180° with respect to the white plate glass surface was measured. Values exceeding 3.0 N / cm were marked as 〇, values between 1.0 and 3.0 N / cm were marked as △, and values less than 1.0 N / cm were marked as ×.

[0041] Total light transmittance: Using the above evaluation plate glass, it was measured using a haze meter Haze-gard2 manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with JIS K7361-1. The glass value was subtracted.

[0042] Haze: Using the above evaluation plate glass, it was measured using a haze meter Haze-gard2 manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with JIS K7361-1. The glass value was subtracted.

[0043] b* value: Using the above evaluation plate glass, it was measured using an ultraviolet-visible spectrophotometer V-770DS (measurement software: VWST-964) manufactured by JASCO Corporation, in accordance with JIS A5759. The evaluation was marked as 〇 when the total light transmittance was 90% or more, the haze was 0.3% or less, and the b* value was 0.5 or less, and × otherwise.

[0044] Evaluation results Table 2 JPEG0007851142000002.jpg37135

[0045] The photocurable adhesive compositions in the examples obtained good results in all evaluations, including adhesive strength, total light transmittance, haze, and b* value.

[0046] On the other hand, Comparative Example 1, which did not contain (B), had low adhesive strength, and Comparative Examples 2 and 3, which were ureac synthesized from biomass polyols but had a large Mw, also had low adhesive strength. Furthermore, Comparative Example 4, which was petroleum-derived ureac, had low adhesive strength, and Comparative Example 5 also did not have sufficient adhesive strength; all of these were unsuitable for the present invention.

Claims

1. A photocurable adhesive composition comprising: a urethane (meth)acrylate (A) synthesized from a plant-derived polypropanediol (a1), an alicyclic polyisocyanate (a2), and a (meth)acrylate (a3) ​​having a hydroxyl group; a (meth)acryloyl group-containing compound (B) having a polar group; an alkyl chain-like and / or alicyclic (meth)acrylate (C); and a photopolymerization initiator (D), wherein the weight-average molecular weight of (A) is 1000 to 6000, the amount of (A) relative to the total solid content is 10 to 70% by weight, the amount of (B) is 10 to 60% by weight, and the amount of (C) is 3 to 55% by weight.

2. The photocurable adhesive composition according to claim 1, characterized in that (C) contains an alicyclic (meth)acrylate.

3. The photocurable adhesive composition according to claim 1 or 2, characterized in that (C) has a carbon number of C8 to C16.

4. The photocurable adhesive composition according to any one of claims 1 to 3, characterized in that (B) comprises a (meth)acrylate having a hydroxyl group.

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