JP2008133457A - Photocurable composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocurable composition which gives in a short time adhesion layers excellent in initial adhesiveness and low-temperature impact strength. <P>SOLUTION: The photocurable composition comprises (A) 40 to 70 wt.% of a urethane (meth)acrylate resin having a weight average molecular weight ranging from 20,000 to 45,000 and containing a polyester polyol residue, (B) 20 to 50 wt.% of a urethane prepolymer having an isocyanate group at least one terminal, (C) 2 to 15 wt.% of a compound having at least one polar group and at least one photopolymerizable group, and (D) 1 to 6 wt.% of a photopolymerization initiator, wherein each wt.% is a value based on the total weight of (A), (B), (C) and (D). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a photocurable composition, and in particular, includes a predetermined urethane acrylate resin having a polyester polyol residue as a main agent, and gives a cured film excellent in initial adhesiveness, transparency, and cold resistance, and an adhesive. And a photocurable composition useful for paints and the like.

For the purpose of improving the image of products such as cosmetics, medical products, stationery, accessories, etc., an assembly container with a folded ruled line on a plastic sheet such as amorphous polyethylene terephthalate (A-PET) that has good transparency and rigidity is a product. It is used as a packaging material. As for the bonding of this assembled container, the initial appearance is such that the appearance of the product is highly transparent in terms of the nature of the product, and the process can be shifted to the inspection process of the assembled container including adhesiveness immediately after bonding. There is a demand for an adhesive having excellent adhesiveness.

A reactive hot melt adhesive composition containing an isocyanate group-terminated reactive urethane prepolymer has been disclosed for the bonding of this type of assembly container (Patent Document 1). However, until the adhesive is cured to some extent, unless the adhesive surface is kept pressed with an external force for about 4 hours or more, the adhesive surface peels off and the initial adhesiveness is poor.

On the other hand, there is known a method in which a layer made of amorphous polyethylene terephthalate (PET-G) is provided on the surface of a plastic sheet such as amorphous polyethylene terephthalate (A-PET) and can be easily bonded with a solvent (patent) Document 2), since the solvent causes the surface layer of PET-G to become clouded, the appearance of the packaging container is deteriorated.
Japanese Patent Laid-Open No. 10-265758 Japanese Patent Laid-Open No. 5-117413

  Therefore, the applicant of the present invention invented a photocurable composition containing a predetermined reactive compound for the purpose of providing an adhesive that gives an adhesive layer excellent in initial adhesiveness and transparency in a short time. (Japanese Patent Application Nos. 2005-230832 and 2006-217274).

An object of the present invention is to provide a composition that is more excellent in terms of cold resistance, particularly low temperature impact strength, in addition to initial adhesiveness and transparency.

That is, the present invention is as follows.
(A) A urethane (meth) acrylate resin containing a polyester polyol residue and having a weight average molecular weight of 20,000 to 45,000, in an amount of 40 to 70 wt%,
(B) The urethane prepolymer having an isocyanate group at at least one end in an amount of 20 to 50 wt%,
(C) A photocuring containing a compound having at least one polar group and at least one photopolymerizable group in an amount of 2 to 15 wt%, and (D) a photopolymerization initiator in an amount of 1 to 6 wt%. Sex composition, where each wt% is a value relative to the total weight of (A), (B), (C) and (D).

The composition of the present invention is suitably used for producing a plastic case excellent in cold resistance by giving a cured product excellent in low-temperature impact property by the urethane (meth) acrylate resin (A) containing a polyester polyol residue. Is done.

(A) Urethane (meth) acrylate resin In the present specification, (meth) acrylate includes both acrylate and methacrylate. (A) Urethane (meth) acrylate resin has a styrene-converted weight average molecular weight of 20,000 to 45,000, preferably 30,000 to 45,000 determined by GPC measurement. Moreover, the viscosity of 80 degreeC measured according to JISK-7117-1 is 50,000-300,000 mPa * s, Preferably, it is 100,000-250,000 mPa * s. When the viscosity is less than the lower limit value, the adhesive is likely to protrude during bonding. On the other hand, if the upper limit is exceeded, it may be difficult to apply uniformly and the appearance of the bonded portion may be impaired.

(A) Urethane (meth) acrylate resin is produced by adding (meth) acrylate having an isocyanate group and a reactive group to both ends of polyisocyanate obtained by addition reaction of isocyanate and polyester polyol. Can do. The polyester polyol is obtained by an ester reaction between a dicarboxylic acid such as adipic acid or sebacic acid and a glycol such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-methylpentadiol or hexamethylene glycol. Isocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI), and aliphatic systems such as hexamethylene diisocyanate (HDI) and trimethylhexamethylene diisocyanate (TMHMDI). Examples thereof include alicyclic diisocyanates such as diisocyanates, isophorone diisocyanate (IPDI), and methylenebis (4-cyclohexylisocyanate) (hydrogenated MDI). The (meth) acrylate having a reactive group with an isocyanate group includes hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 1-hydroxybutyl (meth) acrylate. Is used.

上記下限値未満であると、組成物の他の成分との相溶性が悪く、硬化物の透明性が悪い場合がある。一方、上記上限値を越えると、低温特性が悪化し、粘度が高くなる場合がある。上記エステル（１）及びエーテル（２）構造の各々における^１Ｈのピークは、通常、図１に示すように、２〜４．５ｐｐｍに観察される。該範囲におけるピークの積分強度の合計の全積分強度に対する割合が上述の範囲である。 Preferably, (A) urethane (meth) acrylate resin has a ratio of the total integrated intensity of ¹ H peaks of the following ester (1) and ether (2) structures to the total integrated intensity in the ¹ H-NMR spectrum of 33 to 40%, preferably 35-38%.

If it is less than the above lower limit, the compatibility with other components of the composition may be poor, and the transparency of the cured product may be poor. On the other hand, when the above upper limit is exceeded, the low-temperature characteristics may deteriorate and the viscosity may increase. The ¹ H peak in each of the ester (1) and ether (2) structures is usually observed at 2 to 4.5 ppm as shown in FIG. The ratio of the total integrated intensity of the peaks in this range to the total integrated intensity is the above-mentioned range.

式（３）において、重量平均分子量が２０，０００〜４５，０００である範囲内において、ｍは１〜９０、好ましくは１〜１０、より好ましくは１〜４の整数、及びｎは１〜２００、好ましくは１０〜２００、より好ましくは４０〜２００の整数、最も好ましくは４０〜１５０の整数である。また、Ｒ^１、Ｒ^２、Ｒ^３、及びＲ^４は、炭素数２〜１２、好ましくは４〜１０のアルキレン基であり、分岐を有していてもよい。好ましくはＲ^１、Ｒ^２、Ｒ^３、及びＲ^４が、以下に示すアルキレン基である。

More preferably, (A) urethane (meth) acrylate resin is represented by the following formula (3).

In the formula (3), m is an integer of 1 to 90, preferably 1 to 10, more preferably 1 to 4, and n is 1 to 200 within a range where the weight average molecular weight is 20,000 to 45,000. , Preferably 10 to 200, more preferably an integer of 40 to 200, and most preferably an integer of 40 to 150. R ¹ , R ² , R ³ , and R ⁴ are alkylene groups having 2 to 12 carbon atoms, preferably 4 to 10 carbon atoms, and may have a branch. Preferably, R ¹ , R ² , R ³ and R ⁴ are alkylene groups shown below.

(B) Isocyanate group-containing urethane prepolymer (B) The urethane prepolymer is synthesized from a polyester polyol or polyether polyol and a diisocyanate, and has an isocyanate at at least one terminal. Polyester polyols include polyethylene adipate (PEA), polybutylene adipate (PBA), polycaprolactone polyol (PCL) and the like, and polyether polyols include polyoxytetramethylene polyol (PTMG) and polyoxypropylene polyol (PPG). can give. Examples of the diisocyanate include the above-described diisocyanates such as tolylene diisocyanate (TDI). Preferably, it contains an aliphatic polyol-based NCO-terminated urethane prepolymer from the viewpoint of no yellowing after curing and flexibility.

(B) The viscosity at 80 ° C. of the urethane prepolymer is preferably 10 to 5,000 mPa · s, more preferably 100 to 1,000 mPa · s.

(C) a compound having at least one polar group and at least one photopolymerizable group (C) a compound having at least one polar group and at least one photopolymerizable group (hereinafter referred to as “photopolymerization compound”) It is considered that the photopolymerizable group is bonded to the cured product network structure, and the polar group interacts with the base material, particularly PET, thereby improving the initial adhesiveness of the cured product. . Examples of the polar group include a hydroxyl group, an amide, and an ester group, and the photopolymerizable group includes an ethylenically unsaturated bond. Examples of (C) photopolymerizable compounds include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, carbitol (meth) acrylate, polyethylene glycol di (meth) acrylate, and glycerin di (meth). Acrylate containing hydroxyl group such as acrylate, glycerin mono (meth) acrylate, pentaerythritol tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate; dimethylacrylamide, diethylacrylamide, (meth) acryloylmorpholine N-vinylpyrrolidone and the like. Preferably, dimethyl acrylamide and diethyl acrylamide are used.

(D) Photopolymerization initiator As the photopolymerization initiator, known ones can be used, for example, benzophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2 -Methyl-1- [4- (methylnio) phenyl] -2-morpholinopropan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, and 2-hydroxy-2-methyl-1-phenyl-propane-1 -ON. By 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. These photopolymerization initiators may be used in combination of two or more, for example, a photopolymerization initiator excellent in surface curability for thin film coating and a photopolymerization excellent in deep curability for thick coating. By combining the initiator, it is possible to impart excellent curability to the adhesive that cannot be obtained by using a single initiator. In the present invention, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-methyl-1- [4- (methylnio) are used from the viewpoint of storage stability of the blended adhesive and transparency of the adhesive. ) Phenyl] -2-morpholinopropan-1-one is preferred.

(E) Heat stabilizer The composition of the present invention is at least one selected from (E) hindered phenol compounds, tocopherols and tocopherol derivatives in addition to the above (A), (B), (C) and (D). Thermal stabilizers may be included. In general, the heat stabilizer includes quinone, amine, hindered phenol, and natural compounds such as tocopherol and ascorbic acid. Of these, hindered phenol and tocopherol are preferably used. The Examples of hindered phenol heat stabilizers include 2,6-di-t-butyl-p-cresol (BHT), 2,6-di-t-butyl-4-ethylphenol, pentaerythritol tetrakis- [methylene-3. -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate, tris (3 , 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), and octadecyl 3,5-di-tert-butyl-4- And hydroxyhydrocinnamate. Examples of the tocopherol system include α-tocopherol, γ-tocopherol, and δ-tocopherol. Among these, 2,6-di-t-butyl-p-cresol (BHT), pentaerythritol tetrakis- [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate and d- and dl-α-tocopherol are preferred. Pentaerythritol tetrakis- [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinna, under the trade name Irganox 1010. The mate is commercially available from Ciba Specialty Chemicals as Irganox 1076.

The blending ratios of the above (A) to (E) are (A) 40 to 70 wt%, preferably 45 to 60 wt%, (B) 20 to 50 wt%, preferably 30 to 45 wt%, based on the total weight of these components. (C) 2-15 wt%, preferably 6-12 wt%, (D) 1-6 wt%, preferably 2-4 wt%, (E) 0.01-3 wt%, preferably 0.05-0.3 wt% %. When (A) is less than the lower limit or exceeds the upper limit, the initial adhesiveness immediately after light irradiation tends to be weakened. When (B) is less than the lower limit, the adhesiveness over time is weakened, and when (B) exceeds the upper limit of the previous period, the initial adhesiveness immediately after light irradiation tends to be weakened. When (C) is less than the lower limit, the initial adhesiveness becomes weak, and when it exceeds the upper limit of the previous period, the adhesiveness at low temperatures tends to become weak. When (D) is less than the lower limit, the initial adhesiveness becomes weak, and when it exceeds the upper limit of the previous period, the adhesiveness at low temperatures tends to become weak.

In addition to (A) to (E), a reactive diluent and various additives may be included as long as the object of the present invention is not impaired. Examples of the reactive diluent include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate exemplified for (C), and examples of the additive include a leveling agent. Moreover, you may mix | blend a coloring agent and a pigment for a paint use. Moreover, you may add a photosensitizer, a dispersing agent, a plasticizer, a filler, an antifoamer, an antifoamer, an electroconductive filler, a polymerization inhibitor, an ultraviolet absorber etc. as needed.

In the composition of the present invention, (A), (B), (C) and (D), preferably (E), and other additives are mixed using a known mixer such as a homomixer. Can be prepared. After mixing, it is preferable to perform a defoaming treatment with a planetary stirrer, a filter or the like. Further, only (D) may be mixed immediately before use.

  The resulting composition can be used to bond various plastic sheets. Examples of the plastic include polyesters such as polyester terephthalate (PET), polylactic acid (PLA), and polypropylene (PP).

The photocurable composition of the present invention can be cured by, for example, irradiating a high-pressure mercury lamp after being applied by a dispenser for hot melt adhesive. Typically, the curing energy is about 250 mJ / cm ² , cures immediately after light irradiation, and has excellent initial adhesiveness.

  As shown in FIG. 5, the obtained cured product has two peaks in loss tangent (tan δ) measured in dynamic viscoelasticity measurement between −150 ° C. and 150 ° C. FIG. 5 is a chart showing two tan δ peaks of a cured product obtained from the composition of Example 1 described later. Among them, the peak apex on the low temperature side exists at a temperature lower than 0 ° C. and −30 to −70 ° C. Furthermore, it has been found that tan δ at the peak apex is preferably 0.1 to 0.5 in terms of transparency. The peak on the low temperature side is considered to be due to the polyester polyol segment, and this is considered to result in excellent low temperature impact resistance of the cured product. In the present invention, the low-temperature impact property is evaluated by a drop test, and details thereof are described in Examples.

Examples Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto. In the examples, the term “parts” means parts by weight. The raw materials used are as follows.
Raw material (A) urethane (meth) acrylate resin used in Examples :
Examples 1-3, 7, 8, Reference Examples 1, 2: MJ-11, Mw 37,000-43,000, manufactured by Negami Kogyo Co., Ltd. Example 4: MJ-12, Mw 23,000-27,000, Example 5: manufactured by Negami Kogyo Co., Ltd. Example 5: MJ-13, Mw 30,000-33,000, manufactured by Negami Kogyo Co., Ltd. Example 6: KHP-17, Mw 33,000-37,000, manufactured by Negami Kogyo Co., Ltd. (B) Urethane prepolymer curing agent: Takenate XA-18 (aliphatic), manufactured by Mitsui Takeda Chemical Co., Ltd.)
(C) Photocurable compound: Dimethylacrylamide (DMAA), manufactured by Kojin Co., Ltd. (D) Photopolymerization initiator:
Irgacure 651 (trademark), 2,2-dimethoxy-1,2-diphenylethane-1-one

Examples 1 to 8, Reference Examples 1 and 2
Each component shown in Table 1 is blended (wt%) shown in the same table, (B) urethane prepolymer, (A) urethane (meth) acrylate resin, (C) photopolymerizable compound, (D) photopolymerization initiator. The mixture was heated and mixed at 70 ° C. in a homomixer in this order. After a uniform mixture was obtained, defoaming treatment was performed using a planetary stirrer, and the following evaluation was performed. Moreover, the NMR spectrum of each urethane (meth) acrylate resin used is shown in FIGS. A composition was prepared in the same manner as in Example except that Comparative Example 1 was not formulated with (C) and Comparative Example 2 was not blended with (B).

Evaluation Method (1) A 160 cm × 170 cm × 300 μm A-PET sheet with UV ink printed on the front surface and antistatic treatment on the back surface was used as a substrate on which the initial adhesive composition was applied. Each composition is heated, applied to the end of the printed surface of the A-PET sheet with a coating air nozzle at a width of 3 mm, a length of 150 mm and a thickness of 90 μm, and the back side of the other end with a laminating machine Then, the bonded part was immediately irradiated with 250 mJ / cm ² of high pressure mercury lamp light, and an adhesive part was immediately formed. After the adhesive part was cooled to room temperature, the adhesive part was twisted by hand, and the initial adhesiveness was evaluated according to the following criteria by visual observation.
A: No peeling occurs.
B: Only the edge part of an adhesion part peels.
C: It peels entirely.

(2) Low temperature impact strength Punched out from an A-PET sheet having a thickness of 300 μm in which a paste margin is provided for a hexahedral case of length (D) 44 mm × width (W) 45 mm × height (H) 162 mm . The margin part was provided on the side part of height (H) 162 mm with a width of about 3 mm, and each composition was applied to the margin part with a length of 155 mm and a thickness of 90 μm, and then pasted together. In this state, the paste margin was placed outside the case. Immediately after bonding, high pressure mercury lamp light was irradiated at 250 mJ / cm ² to immediately form an adhesive portion. The case was held for 24 hours at 23 ° C. and 50 RH%. For evaluation, after placing the case in a low temperature room at -20 ° C for 12 hours, a cylindrical sample weighing 1 kg is put in the case, and the case held in the hand from a height of 1 m is placed on a concrete surface with little unevenness. It was allowed to fall freely. The drop test was performed 30 times for each condition. In Example 7, a double-sided corona-treated PP was used in place of the A-PET sheet, and in Example 8, a double-sided untreated polylactic acid sheet was used.
A: There is no peeling of glue.
B: One or more pieces of glue peeling of 1 mm or more and less than 5 mm were confirmed.
C: One or more pastes of 5 mm or more were confirmed.

(3) Room temperature peel strength (2) Using a bonded part (width 3 mm) of the sample for measuring low temperature impact strength, the strength by a T-type peel test (tester: INTESCO IM20) under the conditions of 50 mm / min and 23 ° C. Was measured. When there was a yield point, the peel strength was defined as the intermediate value between the yield point and the average peel strength after the yield point. When there was no yield point, the average value was taken as the strength.

(4) Low-temperature peel strength (2) Using a T-type peel test (tester: INTESCO IM20) under the conditions of 50 mm / min and −20 ° C. using the bonded portion (width 3 mm) of the sample for measuring low temperature impact strength. The strength was measured. When there was a yield point, the peel strength was defined as the intermediate value between the yield point and the average peel strength after the yield point. When there was no yield point, the average value was taken as the strength.

  As shown in Table 1, each of the compositions of Examples gave a cured product excellent in initial adhesiveness and low temperature impact strength. The composition of Example 7 is the same as the composition of Example 1, but the base material used was a PP sheet, and the base material was cracked during the measurement of the low temperature peel strength. The peel strength was low. The composition of Reference Example 1 lacked (C) the photopolymerizable compound and had low peel strength. The composition of Reference Example 2 lacked the (B) urethane prepolymer, had a high viscosity, and was preheated to about 100 ° C. when applied to the paste margin. It is considered that the activity of (D) the photopolymerization initiator was reduced by this heating.

  The photocurable composition of the present invention is useful for an instantly curable cold-resistant adhesive and a paint.

2 is an H-NMR spectrum of a urethane (meth) acrylate resin used in Example 1. 2 is an H-NMR spectrum of a urethane (meth) acrylate resin used in Example 4. 2 is an H-NMR spectrum of a urethane (meth) acrylate resin used in Example 5. 2 is an H-NMR spectrum of a urethane (meth) acrylate resin used in Example 6. 2 is a chart of a loss tangent (tan δ) curve of a cured product obtained from the composition of Example 1.

Claims (10)

(A) A urethane (meth) acrylate resin having a weight average molecular weight of 20,000 to 45,000 and containing a polyester polyol residue, in an amount of 40 to 70 wt%,
(B) a urethane prepolymer having an isocyanate group at at least one end in an amount of 20 to 50 wt%;
(C) a photocuring containing a compound having at least one polar group and at least one photopolymerizable group in an amount of 2 to 15 wt%, and (D) a photopolymerization initiator in an amount of 1 to 6 wt%. Sex composition, where each wt% is a value relative to the total weight of (A), (B), (C) and (D). (A) Urethane (meth) acrylate resin is a ratio of the total integrated intensity of ¹ H peaks of the ester structure of the following formula (1) and the ether structure of the formula (2) in the ¹ H-NMR spectrum to the total integrated intensity The composition according to claim 1, which is 33 to 40%.

(A) Urethane (meth) acrylate resin is shown by following formula (3), The composition of Claim 1 or 2 characterized by the above-mentioned.

(In Formula (3), m is an integer of 1 to 90, n is an integer of 1 to 200, and R ¹ , R ² , R ³ , and R ⁴ are each independently an alkylene group having 2 to 12 carbon atoms. Is) The composition according to claim ³ , wherein R ¹ , R ² , R ³ , and R ⁴ are each a group shown below.

(C) The light according to any one of claims 1 to 3, wherein the compound having at least one polar group and at least one photopolymerizable group is dimethyl (meth) acrylamide and / or diethyl (meth) acrylamide. Curable composition. (B) A urethane prepolymer contains an aliphatic polyol residue, The photocurable composition of any one of Claims 1-4 characterized by the above-mentioned. (D) The photopolymerization initiator is 2,2-dimethoxy-1,2-diphenylethane-1-one and / or 2-methyl-1- [4- (methylnio) phenyl] -2-morpholinopropane-1- The photocurable composition according to any one of claims 1 to 5, which is ON. The adhesive agent containing the composition of any one of Claims 1-6. The coating material containing the composition of any one of Claims 1-6. A box made of a polyester sheet, wherein one end of the polyester sheet and the other end are bonded together with the adhesive according to claim 7.

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