JPH01170679A - Acrylic pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition capable of simultaneously satisfying adhesive force both at ordinary and high temperatures, by blending an acrylic polymer with a specific tackifier resin. CONSTITUTION:A composition obtained by blending (A) an acrylic polymer with (B) at least two components selected from (i) a metallic salt of rosin phenolic resin (preferably 50-100eguiv.% of COOH groups are converted into metallic salt) with (ii) an esterified substance of resin phenolic resin with a polyhydric alcohol (preferably 20-100equiv.% of COOH groups are esterified) and (iii) a reaction product prepared by reacting the rosin phenolic resin with the polyhydric alcohol and a metallic compound or the rosin phenolic resin with the polyhydric alcohol and metallic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an acrylic pressure-sensitive adhesive composition. More specifically, the present invention relates to an acrylic pressure-sensitive adhesive composition that has excellent adhesive strength at room temperature and high adhesive strength at about 50 to 100°C.

[Prior art] Pressure-sensitive adhesive compositions used for labels, adhesive tapes, double-sided adhesive tapes, etc., are designed with adhesive properties such as tack and cohesive force, and adhesive strength, taking into account the environment in which they are used. Other requirements include color tone and transparency. For this reason, acrylic pressure-sensitive adhesive compositions containing an acrylic polymer as a main component have conventionally been praised as pressure-sensitive adhesive compositions.

When the acrylic pressure-sensitive adhesive composition is used at room temperature, the acrylic polymer alone can provide sufficient adhesive strength. However, when the acrylic pressure-sensitive adhesive composition is used for applications that are exposed to high temperatures, such as automobile engines, weak electrical parts, and automobile bodies, the adhesive strength is limited to only the adhesive strength at room temperature. Adhesive strength at high temperatures of about 50 to 100°C is required, but since the adhesive strength decreases as the temperature rises, it is difficult to use acrylic polymers alone.

Therefore, acrylic pressure-sensitive adhesive compositions generally include rosin ester, C9 petroleum resin, etc. to improve adhesive strength.
A tackifying resin such as a so-called pure monomer resin represented by a terpene resin or a styrene copolymer is blended.

However, although the acrylic pressure-sensitive adhesive composition containing the tackifier resin has improved adhesive strength at room temperature, it has the disadvantage that the adhesive strength significantly decreases as the temperature rises at high temperatures of about 50 to 100°C. Therefore, the tackifying resin is a factor that actually reduces the adhesive strength at high temperatures.

In order to increase adhesive strength at high temperatures, the crosslinking density of the acrylic polymer may be increased by increasing the amount of crosslinking monomer or crosslinking agent, or the use of organometallic compounds such as stannic laurate. Attempts have been made to add .

As mentioned above, the current situation is that acrylic pressure-sensitive adhesive compositions that have excellent adhesive strength at both room temperature and high temperature have not been replaced.

[Problems to be Solved by the Invention] The present invention provides an acrylic pressure-sensitive adhesive composition that exhibits excellent adhesive strength at both room temperature and high temperature without impairing adhesive properties such as tack and cohesion. The purpose is to provide

[Means for Solving the Problems] In view of the above-mentioned problems, the present inventors conducted intensive studies focusing on tackifier resins that are blended into acrylic copolymers, and as a result, found that a specific tackifier resin was used. discovered that all the problems of the prior art could be solved by using
This led to the completion of the present invention.

That is, the present invention provides an acrylic pressure-sensitive adhesive composition comprising an acrylic polymer and a tackifying resin, wherein the tackifying resin is a metal salt of artificial ginphenol resin, CB1.
At least two components selected from a polyhydric alcohol ester of a rosin phenol resin and (C) a reaction product obtained by reacting a rosin phenol resin with a polyhydric alcohol and a metal compound; The present invention relates to an acrylic pressure-sensitive adhesive composition characterized in that it is a reaction product obtained by reacting a hydric alcohol and a metal compound.

[Operations and Examples] In the acrylic pressure-sensitive adhesive composition of the present invention, an acrylic polymer is used as the pace polymer. The composition of the acrylic polymer is not particularly limited, and various known homopolymers or copolymers can be used as they are. As monomers used in the acrylic polymer, various acrylic esters and/or methacrylic esters (hereinafter referred to as (meth)acrylic esters) can be used. Specific examples of such (meth)acrylic esters include (meth)
Examples include methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and these may be used alone or in combination. Furthermore, in order to impart polarity to the resulting acrylic polymer, a small amount of (meth)acrylic acid may be used in place of a portion of the (meth)acrylic acid ester. Further, as a crosslinking monomer, for example, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-methylol (meth)acrylamide, etc. may be used in combination. Furthermore, if desired, other copolymerizable monomers such as vinyl acetate, styrene, etc. may be used in combination to the extent that the adhesive properties such as tack and cohesive force of the (meth)acrylic acid ester polymer are not impaired. These (meta)
There are no particular restrictions on the glass transition temperature of acrylic polymers containing acrylic ester as the main component, but usually -
The temperature is preferably 90 to 0°C, preferably -80 to -10°C. If the glass transition temperature is too high than 0°C, the tack will drop significantly, which is undesirable.

Furthermore, if the temperature is too low than -90°C, the adhesive strength tends to decrease. There are no particular restrictions on the method for producing the acrylic polymer, and various known methods can be employed. For example, it can be easily produced by appropriately selecting a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method. As the radical polymerization initiator, various known initiators such as azo type and peroxide type can be used. Reaction temperature is usually 50-85°C
The extent and reaction time are preferably about 1 to 8 hours. In addition, in the case of solution polymerization, there are no particular restrictions on the solution used; generally, a polar solvent such as ethyl acetate is used.

In the acrylic pressure-sensitive adhesive composition of the present invention, the tackifying resin includes a metal salt of rosin phenol resin (hereinafter referred to as resin hole), a polyhydric alcohol ester of rosin phenol resin (hereinafter referred to as resin [8)] ) and a reaction product obtained by reacting a polyhydric alcohol and a metal compound with a rosin phenol resin (hereinafter referred to as resin (C)) or a resin (C1).
is used. That is, the object of the present invention is achieved by using the tackifier resin.

The rosin phenol resin referred to in this specification refers to rosin and phenols reacted in the presence of an acid catalyst such as sulfuric acid, boron trifluoride, hydrogen chloride, para-toluenesulfonic acid, methanesulfonic acid, etc. may be added, and may be further heated to form a polymer. The molar ratio of rosin to phenol may be l:o, 8 to 1:1.5.

The addition reaction is usually carried out at 130 to 200°C for about 4 to 10 hours, and the polymerization reaction is usually carried out at 250 to 350°C.
It would be best to do it in about 8 hours.

In addition to the above-mentioned rosin phenol resin, sulfuric acid, boron trifluoride, etc. So-called rosin-modified phenolic resins obtained by reacting in the presence of an acid catalyst such as hydrogen chloride, para-toluenesulfonic acid, methanesulfonic acid, etc. can also be included in the concept of rosin phenolic resins referred to in this specification. It can be used effectively in the same way as phenolic resin. The charging ratio for the formaldehyde addition reaction is preferably 1 to 4 moles of phenol to 1 mole of formaldehyde, and this reaction is usually carried out at 40 to 100°C.
It is best to do this for about 5 hours. In addition, the charging ratio for the addition reaction of resol type phenolic resin and rosin is 0.2 to 1.0 to 1 mole of rosin.
The amount should be about 3 mol, and the reaction is usually 200 to 270 mol.
℃ for about 1 to 8 hours.

Hereinafter, in this specification, the rosin phenol resin and the rosin modified phenol resin are collectively referred to as rosin phenol resin.

Examples of the rosin include various known rosins, such as gum rosin, wood rosin, Torura rosin, and polymerized rosin. In addition, phenols include phenol,
Cresol, β-naphthol, para-t-butylphenol,! <Any substance that can be added to rosin, such as laoctylphenol and paranonylphenol, can be used.

The resin (5) is preferably one in which approximately 50 to 100 equivalent % of the carboxyl groups of the rosin phenol resin are metal salts. Therefore, there is no problem even if unreacted rosin phenol resin is contained in the resin holes. Is it the metal chloride rate of all carboxyl groups in the resin holes or 50 equivalents? If it is too small than 6, the improvement in the adhesive strength of the resulting acrylic pressure-sensitive adhesive composition at high temperatures will be small.

The type of metal salt is not particularly limited, but -
valent metal salts are preferred. When a divalent or higher metal salt is used, the viscosity of the resulting acrylic pressure-sensitive adhesive composition tends to become too high, resulting in poor workability. Specific examples of -valent metal salts include lithium salts, sodium salts, potassium salts, etc. Among these, lithium salts are particularly preferred. Furthermore, the type of metal salt used as the base is not particularly limited, but hydroxides of the aforementioned metals are preferred.

The resin holes are manufactured, for example, by the method shown below. That is, rosin phenol resin is dissolved in a soluble solvent such as toluene, xylene, or ethyl acetate, and then a predetermined amount of a metal compound is added to this solution so that the metal chloride rate of the carboxyl group of rosin phenol resin is within the above range. A neutralization reaction is carried out by adding a solution dissolved or decomposed in deionized water (a. After the reaction is complete, the resin pores are replaced by removing the solvent and water.
It is preferable to carry out the heating at ~90°C for about 0.5 to 4 hours.

The resin f8) is preferably one that can be provided by esterifying about 20 to 100 equivalent % of the carboxyl groups of the rosin phenol resin. Therefore, the resin (B) may contain unreacted rosin phenol resin. If the esterification rate of the carboxyl group of the resin (B) is too small than 20 equivalent %, the adhesive strength of the resulting acrylic pressure-sensitive adhesive composition at room temperature decreases.

In the present invention, a polyhydric alcohol is used in the esterification reaction. - If a hydrovalent alcohol is used, the softening point of the resulting resin (B) will be lowered, which is not preferable. The polyhydric alcohol used is not particularly limited, and includes, for example, dihydric alcohols such as ethylene glycol and diethylene glycol, trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane,
Any of the tetrahydric alcohols can be used, such as pentaerythritol, among which glycerin is preferred. Resin (B) is produced, for example, by the method shown below.

That is, rosin phenol resin and rosin phenol are mixed in an inert gas in the presence or absence of an acidic esterification catalyst such as paratoluenesulfonic acid or phosphoric acid or an alkaline esterification catalyst such as lithium hydroxide or magnesium hydroxide. Resin B) can be changed by charging a specified polyhydric alcohol such that the esterification rate of the carboxyl group of the resin is within the above range into a reaction vessel, heating it, and removing water produced by the reaction from the reaction system. .

The heating reaction is usually carried out at 150 to 300°C for about 2 to 15 hours.

Resin (0 is 5 to 80 equivalents, about 96 of the carboxyl groups of the rosin phenol resin are esterified, and 1O to
It is preferable that the total equivalent amount is about 10 equivalent%. Therefore, unreacted rosin phenol resin may be included in the resin (Q). If the esterification rate of the carboxyl group of the resin (C) is much smaller than 5% and 2%, the resulting acrylic The adhesive strength of the pressure-sensitive adhesive composition at room temperature decreases, and if the pressure-sensitive adhesive composition is too large than 80 to 96, the adhesive strength at high temperature decreases.
), if the metal chloride ratio of the carboxyl group is too small than 10%, the adhesive strength at high temperatures will decrease and the
If it is too thick or thicker than 2%, the adhesive strength at room temperature will decrease. The metal compound and polyhydric alcohol used include, for example, the resin hole or resin (B).
It may be similar to that used in the production of. In addition, the manufacturing method of resin (C) is the manufacturing method of resin (2) and the manufacturing method of resin (
The manufacturing method B) may be carried out in any order.

Resin holes thus obtained, resin (B) and resin (C)
It is preferable that the softening point of each of these is about IH to 200°C. If the softening point is too lower than 160°C, the adhesive strength at high temperatures tends to decrease.

Furthermore, if the temperature is too high than 200°C, the tackiness at room temperature tends to decrease.

In the present invention, an adhesive composition containing an acrylic polymer and a tackifying resin is used. The blending ratio of the acrylic polymer and the tackifying resin is 70 to 70 parts of the acrylic polymer in terms of solid content, when the combination of the acrylic polymer and the tackifying resin is 100 parts (parts by weight, the same applies hereinafter). 95
It is preferable to use about 5 to 30 parts of the slate-imparting resin. If the amount of the acrylic polymer used is less than 70 parts, the tackiness will be almost gone and it will be difficult to use it as an adhesive, and if it is too much than 95 parts, the tackifier to be blended will be too low. There is a tendency that the effect of the resin becomes smaller and the adhesive strength at high temperatures decreases. Here, 20% or more, preferably 50% or more of the total number of carboxyl groups in the tackifier resin has reacted with the polyhydric alcohol or metal compound, and the equivalent ratio of the polyhydric alcohol ester and the metal salt is 10% or more. :90 to 90:10. If the ratio of polyhydric alcohol ester is too small than 10, the adhesive strength of the resulting acrylic pressure-sensitive adhesive composition at room temperature will decrease, and if it is too large than 90, the adhesion at high temperature will decrease. Power tends to decrease. Furthermore, when using a mixture of resin holes and resin (B), the specific blending ratio is as follows: 3 to 15 parts of resin holes to about 70 to 95 parts of acrylic polymer in terms of solid content;
2 to 20 parts of resin (B) is preferred. If the number of resin holes is less than 3 parts, the adhesive strength of the resulting acrylic pressure-sensitive adhesive composition at high temperatures will decrease, and if it is more than 15 parts, the adhesive strength at room temperature will decrease. There is a tendency to decrease. On the other hand, if the resin (B) is too less than 2 parts, the adhesive strength at room temperature will be reduced, and if it is too much more than 20 parts, the adhesive strength at high temperature will be reduced. Tend.

In addition, when using a mixture of resin holes and resin (C), a mixture of resin (B) and resin (C) as the tackifying resin, the total amount of the acrylic polymer and the tackifying resin is 1
The blending ratio of the acrylic polymer to the tackifier resin and the ratio of the polyhydric alcohol ester to the metal salt in the tackifier resin may be within the same range as described above.

In the present invention, by blending the specific tackifying resin as described above, an acrylic pressure-sensitive adhesive composition having excellent adhesive strength at room temperature and high temperature, which is the object of the present invention, can be obtained.

This is because the resin (5), which has a high softening point, provides adhesive strength at high temperatures, and on the other hand, the decrease in adhesive strength at room temperature that occurs is supplemented by the use of resin (B). It is considered that the adhesion strength at both of these points is satisfied at the same time.

The acrylic pressure-sensitive adhesive composition of the present invention does not contain a crosslinking agent such as a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin, or an epoxy resin as an essential component, but it does have cohesive strength and heat resistance. It may be used for further improvement. Among these, polyisocyanate compounds are particularly preferred, and any of various known compounds may be used. Specifically, 1,6-hexamethylene diisocyanate, tetramethylene diisocyanate,
Examples include isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, and 4,4-diphenylmethane diisocyanate.

Furthermore, fillers, antioxidants, ultraviolet absorbers, and the like may be added to the acrylic pressure-sensitive adhesive composition of the present invention, if necessary. Moreover, the pressure-sensitive adhesive composition of the present invention can also be used in combination with various known tackifying resins.

The present invention will be explained in more detail with reference to Production Examples, Examples, and Comparative Examples below, but the present invention is not limited to these aspects. In each example, all parts and percentages are based on the amount of fff unless otherwise specified.

Production Example 1 (Production of acrylic polymer) After 90 parts of ethyl acetate was charged into a reaction vessel equipped with a stirring device, a cooling tube, a dropping funnel, and a nitrogen introduction tube, the temperature inside the system was brought to about 80℃ under a nitrogen stream. The temperature was raised to ℃. Next, two dropping funnels were separately charged with a solution consisting of 73 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, and 2 parts of acrylic acid, and a solution consisting of 0.2 parts of benzoyl peroxide and 10 parts of ethyl acetate. from,
The solution was added dropwise into the system over about 4 hours and kept at the same temperature for another 1 hour to complete the polymerization reaction, yielding an acrylic polymer with a resin solid content of 50%. The glass transition temperature of the acrylic polymer was -61'C.

Production Example 2 (Production of acrylic polymer used in Comparative Example 3) Production was performed except that the blending ratio of the acrylic monomers in Production Example 1 was changed to 70 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, and 5 parts of acrylic acid. An acrylic polymer having a resin solid content of 50% was obtained in exactly the same manner as in Example 1. The glass transition temperature of the obtained acrylic polymer was -58°C.

Production Example 3 (Production of lithium salt of rosin phenol resin) In a reaction vessel similar to Production Example 1, rosin phenol resin (manufactured by Arayo Kagaku Kogyo ■, trade name "Tamanol 803 J") 1
00 parts and 150 parts of toluene were charged, stirred and dissolved, and the temperature was raised while stirring until the temperature inside the system reached 80°C. Then, add 4 parts of lithium hydroxide to 4 parts of deionized water in advance.
Add the aqueous solution dissolved in 0 parts, and after the dropwise addition, 8 parts
Neutralization reaction was carried out for 1 hour while keeping the temperature at 0°C. After the reaction was completed, the solvent and water were distilled off under reduced pressure to obtain a lithium salt of rosin phenol resin. The softening point of the resin is 185℃
The lithium chloride rate was 96% (resin A).

Production Example 4 (Production of glycerin ester of rosin phenol resin) In a reaction vessel similar to Production Example 1, rosin phenol resin (manufactured by Arayo Kagaku Kogyo ■, trade name "Tamanol 803 J") 1
After charging 00 parts of glycerin and 3 parts of glycerin, the system was heated under a nitrogen stream until the temperature inside the system reached 240°C. 3 at the same temperature
After reacting for an hour, the temperature was further raised to 275°C, and the reaction was continued at the same temperature for 5 hours. Thereafter, the low boiling point fraction was removed under reduced pressure to obtain a glycerin ester of rosin phenol resin. The softening point of the resin was 17G, 5°C, and the esterification rate was 63% (resin B).

Production Example 5 In a reaction vessel similar to Production Example 1, 10 ml of rosin phenol resin (manufactured by Arayo Kagaku Kogyo ■, trade name "Tamanol 803 J") was placed.
After charging 0 parts and 1.5 parts of glycerin, the system was heated under a nitrogen stream until the internal temperature reached 240°C. After reacting at the same temperature for 3 hours, the temperature was further raised to 275°C and the reaction was continued at the same temperature for 8 hours. Thereafter, the low boiling point fraction was removed under reduced pressure to obtain a glycerin ester of rosin phenol resin. Further, 100 parts of the obtained glycerin phenol resin ester and 150 parts of toluene were charged into a similar reaction vessel, and while melting, the temperature inside the system was raised to 8.
It was heated until it reached 0°C.

Then, add 2 parts of lithium hydroxide to 40 parts of deionized water in advance.
Add the aqueous solution dissolved in 1 part and keep warm at 80°C.
A time neutralization reaction was performed. After the reaction is complete, the solvent and water are distilled off under reduced pressure to remove the glycerin from the rosin phenol resin.
A reaction product with lithium hydroxide was obtained. The resulting resin had a softening point of 189.5°C, an esterification rate of 35% and a lithium chloride rate of 58% and 2% (resin C).

Production Example 6 Into the same reaction vessel as in Production Example 1, 100 parts of glycerin ester of rosin-modified phenol resin (manufactured by Arayo Kagaku Kogyo ■, trade name "Tamanol 379 J") and 100 parts of toluene were charged. It was heated until the temperature reached 80°C. Then, an aqueous solution in which 2 parts of lithium hydroxide had been dissolved in 40 parts of deionized water was added, and the temperature was kept at 80°C to conduct a neutralization reaction for 1 hour. The reaction was completed. Thereafter, the solvent and water were distilled off under reduced pressure to obtain a reaction product of the rosin phenol-modified resin with glycerin and lithium hydroxide.

The resulting resin had a softening point of 183.0°C, an esterification rate of 70 equivalents of 96, and a lithium chloride rate of 20 equivalents % (Resin C).

Example 1 80 parts (solid content equivalent) of the acrylic polymer obtained in Production Example 1, 10 parts of the lithium salt of the rosin phenol resin obtained in Production Example 3, and the glycerin of the rosin phenol resin obtained in Production Example 4 After thoroughly kneading 10 parts of the ester, 8.2 parts of a polyisocyanate compound (trade name: Coronate LJ, manufactured by Nippon Polyurethane Co., Ltd.) was added to obtain a crosslinked acrylic pressure-sensitive adhesive composition. The resulting cross-linked acrylic pressure-sensitive adhesive composition was applied to a polyethylene film with a thickness of 38 mm using a dice applicator so that the dry film thickness was approximately 30 mm, and then the solvent in the adhesive composition was applied. was removed to create a tape with an adhesive thickness of 30 μm,
Various performance tests were conducted using the following methods. Table 1 shows the composition and performance test results of the obtained acrylic pressure-sensitive adhesive composition.

Examples 2 to 9 Various crosslinked acrylic pressure-sensitive adhesives were prepared in exactly the same manner as in Example 1, except that the formulations of the acrylic polymer and tackifier resin were changed as shown in Table 1. The composition was prepared, a performance test tape was prepared, and a performance test was conducted.

Table 1 shows the composition of the obtained acrylic pressure-sensitive adhesive composition and the results of performance tests.

Comparative Examples 1 to 5 Various crosslinked acrylic pressure-sensitive adhesives were prepared in exactly the same manner as in Example 1, except that the formulations of the acrylic polymer and tackifying resin were changed as shown in Table 1. The composition was prepared, a performance test tape was prepared, and a performance test was conducted.

Table 1 shows the composition and performance test results of the obtained acrylic pressure-sensitive adhesive composition.

(Performance test of acrylic pressure-sensitive adhesive composition) Example 1~
After aging the tapes obtained in Comparative Examples 9 and Comparative Examples 1 to 5 for 3 days, the performance was evaluated by the following test method.

(Room temperature adhesive strength) The obtained tape (251 x 100 mm) was pasted on a stainless steel plate and tested at 20°C for 30 minutes using a universal tensile tester.
180” peel strength (k
g/25m weight) was measured.

(High temperature adhesive strength) The obtained tape (25no+X I00mn+) was pasted on a stainless steel plate and tested at 80°C using a universal tensile test.
, 180° peel strength (k
g/25mm) was measured.

(Cohesive force) The obtained tape (25 mm x 25 n+m) was attached to a stainless steel plate, a load of 1 kg was applied at 40° C., and the distance deviated after 1 hour was measured.

(High-temperature cohesive force) The obtained tape (20 mm x 20+1101) was attached to a stainless steel plate, a load of 1 kg was applied at 80°C, and the time Mj until the weight fell was determined.

(Tack) Using the obtained tape, the contact speed and separation speed were determined to be 10 μ/sec, and the contact load was 1 using a probe tack measuring machine according to the ASTM D-2979r probe tack method.
The peeling resistance force was measured at 00g/ci and a contact time of 1 second.

[Margins below] [Effects of the Invention] The acrylic pressure-sensitive adhesive composition of the present invention has excellent adhesive strength at room temperature and high temperature while satisfying required performances such as cohesive force and tack. be. Therefore, the acrylic pressure-sensitive adhesive composition of the present invention can be used for labels, sheets, adhesive tapes, double-sided adhesive tapes, etc. used in places exposed to high temperatures such as automobile engines, weak electrical parts, and automobile bodies. It is particularly suitable for use.

Patent applicant: Arakawa Chemical Industry Co., Ltd.

Claims (1)

[Scope of Claims] 1. An acrylic pressure-sensitive adhesive composition comprising an acrylic polymer and a tackifying resin, the tackifying resin comprising (A) a metal salt of a rosin phenol resin, and (B) a rosin. At least two components selected from a polyhydric alcohol ester of a phenol resin and (C) a reaction product obtained by reacting a rosin phenol resin with a polyhydric alcohol and a metal compound, or (C) a rosin phenol resin and a polyhydric alcohol. An acrylic pressure-sensitive adhesive composition characterized by being a reaction product obtained by reacting a metal compound with