JP2614682B2 - Acrylic adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition used for, for example, a label, a pressure-sensitive adhesive tape or sheet, and more particularly, to an excellent adhesive property to a soft vinyl chloride resin containing a stabilizer. The present invention relates to an acrylic pressure-sensitive adhesive composition which can shorten the aging time and can therefore increase the productivity of labels, pressure-sensitive adhesive tapes or sheets.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesive tapes or sheets having a pressure-sensitive adhesive layer formed of an acrylic pressure-sensitive adhesive composition formed on one surface of a substrate made of paper or synthetic resin have been widely used. However, when the base material of the pressure-sensitive adhesive tape or sheet is composed of a film mainly composed of a soft vinyl chloride resin containing a stabilizer, the adherend is made of a soft vinyl chloride resin, and the adhesive tape is Alternatively, when a sheet is stuck, or when a soft vinyl chloride resin product is joined with a double-sided adhesive tape, there has been a problem that the adhesive performance is significantly reduced with time. This is because the stabilizer in the soft vinyl chloride resin migrates into the pressure-sensitive adhesive layer with the passage of time and chemically reacts with the functional groups in the pressure-sensitive adhesive, particularly the carboxyl groups, so that the crosslinking in the pressure-sensitive adhesive excessively proceeds. This is because the adhesive performance is reduced. To solve the above problems, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 3-22884 discloses an adhesive in which a sequestering agent is blended with an acrylic adhesive to prevent the metal stabilizer in the soft vinyl chloride resin from migrating to the adhesive side.

[0003] On the other hand, PSA compositions containing a polyisocyanate compound as a cross-linking agent in an acrylic copolymer using a monomer containing a hydroxyl group as a cross-linking starting point are known, and effective PSA properties can be expected. However, the adhesive properties of the adhesive composition, especially heat resistance,
After the pressure-sensitive adhesive composition is cast on a substrate, it does not develop sufficiently unless it is aged at room temperature for 5 to 7 days or is aged at a temperature of about 40 to 80 ° C. for 8 to 24 hours. Therefore, after casting the adhesive, before the substrate is subjected to secondary processing such as slitting, cutting or punching, the substrate on which the adhesive composition has been cast must be deposited in a factory for a long time. Did not. As described above, conventionally, a pressure-sensitive adhesive composition that can prevent a decrease in pressure-sensitive adhesive performance due to migration of a stabilizer in a soft vinyl chloride resin and that can exhibit sufficient heat resistance by aging for a short time is provided. Despite the craving,
It did not yet exist.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to satisfy the above-mentioned demands, to provide an excellent adhesive property to a soft vinyl chloride resin, and to achieve a sufficient productivity in which sufficient heat resistance can be exhibited by aging for a short time. An object of the present invention is to provide an excellent acrylic pressure-sensitive adhesive composition.

[0005]

The acrylic pressure-sensitive adhesive composition of the present invention comprises an alkyl acrylate having an alkyl group having 2 to 12 carbon atoms, a nitrogen-containing vinyl monomer, and caprolactone-modified (meth) acrylic acid. Ester- modified caprolactone modified (meth) acrylic acid
The copolymerization ratio of the ester is 0.1 to 2% by weight, and
Whether the polymerizable unsaturated carboxylic acid is not copolymerized at all
Or copolymerized at a ratio of 0.5% by weight or less even if copolymerized
The acrylic copolymer resins which are engaged, the polyisocyanate compound is characterized by being formulated as a crosslinking agent, thereby solves the above problems.

Examples of the alkyl acrylate which can be used in the present invention include ethyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate,
Examples include nonyl acrylate and lauryl acrylate. Examples of the nitrogen-containing vinyl monomer include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, and dimethylaminoethyl methacrylate.

[0007] The copolymerization ratio of the nitrogen-containing vinyl monomer in the acrylic copolymer resin is preferably 3 to 30% by weight, more preferably 5 to 20% by weight. If the content is less than 3% by weight, the cohesive force is small, and when a product is formed, the pressure-sensitive adhesive protrudes, and the holding power and creep resistance are reduced. On the other hand, when the content exceeds 30% by weight, the pressure-sensitive adhesive becomes too hard, and the pressure-sensitive adhesive strength particularly at a low temperature is lowered, and the pressure-sensitive adhesive becomes unsuitable.

Furthermore, the above-mentioned modified caprolactone (meta)
The acrylate is a compound represented by the following formula (I). When the compound represented by the formula (I) is copolymerized with another polymerizable vinyl compound, the functional group —OH group can move more flexibly than the polymer main chain —O— ( COC ₅ H ₁₀ O) n - via a coupling, and high reactivity due to the presence in the remote location. Therefore,-
Since the OH group quickly reacts with the —N ＝ C ＝ O group of the polyisocyanate compound used as the cross-linking agent, the aging time required for developing the adhesive properties, particularly the heat resistance, can be greatly reduced.

[0009]

Embedded image

In the above formula (I), R represents H or CH ₃ , and n is an integer of 1-5. The modified caprolactone (meth) acrylate represented by the above formula (I) is contained in the range of 0.1% by weight to 2% by weight based on all the monomers constituting the acrylic copolymer resin.
It is necessary. If the amount is less than 0.1% by weight, the degree of crosslinking of the pressure-sensitive adhesive does not increase and sufficient creep characteristics cannot be obtained. If the amount exceeds 2% by weight, gelation of the pressure-sensitive adhesive solution is caused, and the practicality is reduced. Because.

A polymerizable unsaturated carboxylic acid such as (meth) acrylic acid, itaconic acid, fumaric acid, or maleic acid, particularly acrylic acid is used to balance the physical properties of the pressure-sensitive adhesive.
Usually an essential component. However, when the content of the polymerizable unsaturated carboxylic acid exceeds 0.5% by weight of the entire monomers constituting the acrylic copolymer resin, the pressure-sensitive adhesive composition containing the acrylic copolymer resin as a main component will not be used. When the pressure-sensitive adhesive tape or sheet prepared by using the above is affixed to a soft vinyl chloride resin, the stabilizer and the polymerizable unsaturated carboxylic acid in the soft vinyl chloride resin which have been transferred from the soft vinyl resin to the pressure-sensitive adhesive layer with time are used. Causes a chemical reaction. As a result, the crosslinking proceeds extremely in the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive properties are significantly reduced.

Therefore, the pressure-sensitive adhesive composition of the present invention preferably does not contain the above-mentioned polymerizable unsaturated carboxylic acid. Even if the above-mentioned polymerizable unsaturated carboxylic acid is copolymerized, It is necessary that the content of the unsaturated carboxylic acid is 0.5% by weight or less of the whole monomers constituting the acrylic copolymer resin, that is, the content is substantially not contained.

The acrylic copolymer resin used in the pressure-sensitive adhesive composition of the present invention can be obtained by any polymerization method such as solution polymerization or bulk polymerization. The monomer and the caprolactone-modified (meth) acrylic acid ester can be easily obtained by dissolving in a suitable solvent such as ethyl acetate, for example, and performing a solution polymerization method using a polymerization initiator. Further, the alkyl acrylate, a nitrogen-containing vinyl monomer,
A solvent-free liquid mixture comprising a caprolactone-modified (meth) acrylic acid ester, a photopolymerization initiator, and a photoactive crosslinking agent is applied to a support, and polymerized by irradiating ultraviolet light in an inert gas such as nitrogen to form an adhesive tape. It is also possible to get.

In the pressure-sensitive adhesive composition of the present invention, a polyisocyanate compound is compounded as a crosslinking agent with the acrylic copolymer resin. Examples of the polyisocyanate compound that can be used include tolylene diisocyanate or a hydride thereof or an adduct of tolylene diisocyanate with trimethylolpropane, triphenylmethane triisocyanate, methylene bis-di-phenyl isocyanate or a hydride thereof, hexamethylene diisocyanate, Examples include xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and polymers having two or more isocyanate groups in the molecule, such as polymers thereof.

The polyisocyanate compound is effective in maintaining the balance of the adhesive properties of the acrylic copolymer resin, such as the adhesive strength, cohesive strength and tackiness. The amount of the polyisocyanate compound is suitably in the range of about 0.1 to 2 parts by weight based on 100 parts by weight of the acrylic copolymer resin. If the amount is less than 0.1 part by weight, the effect of blending the polyisocyanate compound, that is, the effect of improving the balance of adhesive properties is not sufficient. If the amount exceeds 2 parts by weight, the crosslinking degree of the adhesive becomes too high. This is because a sufficient adhesive strength cannot be obtained. In the acrylic pressure-sensitive adhesive composition of the present invention, in addition to the acrylic copolymer resin and the polyisocyanate compound, for example, a petroleum resin, a terpene resin, a rosin resin, and An appropriate additive such as a tackifier resin such as a malonindene resin or a phenol resin, or various stabilizers or fillers may be blended.

[0016]

In the acrylic pressure-sensitive adhesive composition of the present invention, a caprolactone-modified (meth) acrylic acid ester is added to the acrylic copolymer resin as a main component in a copolymerization ratio of 0.1 to 0.1.
Contained in the range of 2% by weight , and the —OH group of the caprolactone-modified (meth) acrylic acid ester quickly reacts with the —N ＝ C ＝ O group of the polyisocyanate compound as a cross-linking agent. In particular, the aging time required to develop heat resistance is greatly reduced. Also,
The pressure-sensitive adhesive composition of the present invention has no polymerizable unsaturated carboxylic acid such as acrylic acid,
Even if they are mixed, they are copolymerized at a ratio of 0.5% by weight or less.
I have. Accordingly, when the polymerizable unsaturated carboxylic acid is brought into contact with the soft vinyl chloride resin, excessive crosslinking caused by the chemical reaction between the stabilizer and the polymerizable unsaturated carboxylic acid, which have migrated from the soft vinyl chloride resin, does not occur. Therefore, even if the pressure-sensitive adhesive composition of the present invention is brought into contact with a substrate or adherend made of a soft vinyl chloride resin, there is no possibility that the pressure-sensitive adhesive properties will decrease over time.

[0017]

EXAMPLES The present invention will be clarified below by giving Examples and Comparative Examples of the present invention. Example 1 In a separable flask equipped with a condenser, a stirrer, and a thermometer, 94.8 parts by weight of acrylate acrylate, 5 parts by weight of N-vinylpyrrolidone, and a modified caprolactone (meth) acrylate (Daicel Chemical Co., Ltd. Trade name: Praxel FM-2D) 0.2 parts by weight was dissolved in ethyl acetate such that the total amount of the monomers was 55/45 by weight with respect to ethyl acetate, and a polymerization initiator was added to the obtained solution. 0.062 parts by weight of benzoyl peroxide was added. The mixed solution was stirred at 80 ° C. for 8 hours under nitrogen reflux to carry out a polymerization reaction to obtain an adhesive solution, ie, an acrylic copolymer resin solution.

0.2% by weight of the above acrylic copolymer resin solution as a crosslinking agent, trade name: Coronate L (a 55% by weight solution of an adduct of tolylene diisocyanate and trimethylolpropane), manufactured by Nippon Polyurethane Industry Co., Ltd. And the pressure-sensitive adhesive composition of Example 1 was prepared. The pressure-sensitive adhesive composition obtained as described above is coated on one surface of a polyester film having a thickness of 38 μm so that the thickness after drying becomes 25 μm, and then dried at a temperature of 110 ° C. for 5 minutes. I got

Example 2 An adhesive tape was obtained in the same manner as in Example 1 except that the amount of Coronate L as a crosslinking agent was changed to 1.5 parts by weight. Example 3 A pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the amount of the caprolactone-modified (meth) acrylic acid ester (manufactured by Daicel Chemical Industries, Ltd., trade name: Praxel FM-2D) was 1.5 parts by weight. Obtained. Example 4 An adhesive tape was obtained in the same manner as in Example 3, except that the amount of Coronate L as a crosslinking agent was changed to 1.5 parts by weight.

Comparative Example 1 An adhesive tape was obtained in the same manner as in Example 4, except that 2-hydroxyethyl methacrylate was used instead of the modified (meth) acrylic acid ester of caprolactone. Comparative Example 2 Adhesion was carried out in the same manner as in Example 4 except that the amount of the caprolactone-modified (meth) acrylic acid ester (manufactured by Daicel Chemical Industries, Ltd., trade name: Praxel FM-2D) was 0.05 parts by weight. I got the tape.

Comparative Example 3 A pressure-sensitive adhesive tape was prepared in the same manner as in Example 4 except that the amount of the modified caprolactone (meth) acrylate, Daicel Chemical Co., Ltd., trade name: Praxel FM-2D was changed to 10 parts by weight. I got Comparative Example 4 93.8 parts by weight of butyl acrylate, 5 parts by weight of N-vinylpyrrolidone, 1 part by weight of acrylic acid, and caprolactone-modified (meth) acrylic acid ester (trade name: Plaxel FM-2D, manufactured by Daicel Chemical Co., Ltd.) A pressure-sensitive adhesive tape was obtained in the same manner as in Example 4, except that an acrylic copolymer resin solution was obtained using 0.2 parts by weight.

Comparative Example 5 Comparative Example 4 was repeated except that the amount of the caprolactone-modified (meth) acrylate, Daicel Chemical Co., Ltd., trade name: Praxel FM-2D was 1.5 parts by weight.
In the same manner as in the above, an adhesive tape was obtained. Table 1 shows the compositions of the pressure-sensitive adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 5.

[0023]

[Table 1]

In Table 1, BA represents butyl acrylate, Vp represents N-vinylpyrrolidone, and AAc represents acrylic acid.

Evaluation Each of the pressure-sensitive adhesive tapes obtained in Examples 1 to 4 and Comparative Examples 1 to 5 has the following SP adhesive strength, holding power, peeling strength against soft vinyl chloride (with time), and peeling strength against soft vinyl chloride (with time). ) Holding power was measured and evaluated in the following manner. Table 2 shows the results. SP adhesive strength: SUS according to JIS Z0237
15mm adhesive tape on stainless steel plate made of -304
The laminate was bonded by width, and the 180 ° peel strength after a lapse of 20 minutes at a temperature of 23 ° C. was measured at a pulling rate of 300 mm / min. Holding force: SUS-30 in accordance with JIS Z0237
An adhesive tape of 20 mm × 20 mm was stuck to a stainless steel plate made of No. 4 and placed in a thermostat at 80 ° C. with the adhesive tape facing down, a 1 kg suspension load was applied, and the tape displacement or drop time after 1 hour was measured. .

[0034] Peeling force against soft vinyl chloride (aging): 50 parts by weight of dioctyl phthalate as a plasticizer and 15 parts by weight of calcium carbonate as a stabilizer and filler are mixed with 100 parts by weight of polyvinyl chloride having a polymerization degree of 1100. Adhesive tape with a width of 15 mm is bonded to a 5 mm thick soft vinyl chloride plate having the composition
The peel strength was measured at a pulling speed of 300 mm / min. A 20 × 20 mm adhesive tape was stuck to the soft vinyl chloride plate used for the holding force against soft vinyl chloride (temporal), and the shear holding force at 40 ° C. was measured by applying a load of 500 g. The SP adhesive force, the holding force, the peeling force against soft vinyl chloride and the holding force against soft vinyl chloride were measured after preparing an adhesive tape and allowed to stand at room temperature for 24 hours. Further, the retention of soft vinyl chloride over time was measured after leaving each adhesive tape in an 80 ° C. constant temperature bath for one week.

[0027]

[Table 2]

As is clear from Table 2, the adhesive tapes of Comparative Examples 1 and 2 were left at room temperature for 24 hours,
It can be seen that cohesive failure occurs in both cases of sticking to a stainless steel plate and sticking to a soft vinyl chloride plate, and it is not possible to realize sufficient adhesive physical properties. Comparative Example 3
Is a modified caprolactone (meth) acrylate manufactured by Daicel Chemical Co., Ltd., trade name: Placcel FM-
Since the blending ratio in the 2D acrylic copolymer resin was out of the range of the present invention, which was 10 parts by weight, gelation occurred during the polymerization, and a sufficient pressure-sensitive adhesive tape that could be used for each of the above measurements could not be obtained. .

Further, in the pressure-sensitive adhesive tapes of Comparative Examples 4 and 5, 1 part by weight of acrylic acid was compounded as a polymerizable unsaturated monomer.
It can be seen that, after leaving at 80 ° C. for one week, the peeling force and the holding force are significantly reduced. On the other hand, in Examples 1 to 4, the adhesive force and the cohesive force show sufficient immediately after the coating, and even after being stuck to a soft vinyl chloride plate and left at a high temperature for a long time, the peel force and It can be seen that the holding force can be maintained at a sufficient value.

[0030]

As described above, in the acrylic pressure-sensitive adhesive composition of the present invention, an alkyl acrylate having an alkyl group having 2 to 12 carbon atoms, a nitrogen-containing vinyl monomer, and caprolactone-modified (meth) acrylic acid Ester- modified caprolactone modified (meth) acrylic acid
The copolymerization ratio of the ester is 0.1 to 2% by weight, and
Whether the polymerizable unsaturated carboxylic acid is not copolymerized at all
Or less than 0.5% by weight even if copolymerized
Acrylic copolymer resin is used as a crosslinking agent
Due to the compounding of the polyisocyanate compound, even when applied to a substrate made of a soft vinyl chloride resin or affixed to an adherend made of a soft vinyl chloride resin, the adhesive performance decreases with time. It is possible to provide a pressure-sensitive adhesive which is difficult, exhibits sufficient pressure-sensitive adhesive properties immediately after use, and can exhibit sufficient heat resistance even after aging for a short time. Therefore, according to the present invention, a label using a substrate made of a soft vinyl chloride resin, a pressure-sensitive adhesive tape or sheet, and a pressure-sensitive adhesive composition that is optimal for an adhesive application using a vinyl chloride resin as an adherend, with high productivity. It will be possible to supply it with it.

Claims (2)

(57) [Claims] 1. An alkyl acrylate having an alkyl group having 2 to 12 carbon atoms, a nitrogen-containing vinyl monomer, and a compound represented by the following formula (I) (wherein, in the formula (I),
R represents H or CH ₃ , and n represents an integer of 1 to 5. ) Caprolactone-modified (meth) acrylic acid ester and copolymerized with said caprolactone-modified (meth) acrylic acid ester.
The copolymerization ratio of the ter is 0.1 to 2% by weight, and
The unsaturated carboxylic acid is not copolymerized at all or
Even if copolymerized, it is copolymerized at a ratio of 0.5% by weight or less.
An acrylic pressure-sensitive adhesive composition comprising: an acrylic copolymer resin; and a polyisocyanate compound as a crosslinking agent. Embedded image 2. The method according to claim 1, wherein the nitrogen-containing vinyl monomer is N-vinyl alcohol.
Rupyrrolidone, N-vinylcaprolactam, acryloy
Rumorpholine and dimethylaminoethyl methacrylate
At least one of the above, and the acrylic copolymer
Copolymerization ratio of nitrogen-containing vinyl monomer in
The acrylic viscosity according to claim 1, which is 3 to 30% by weight.
Adhesive composition.