JPH059450A - Acrylic pressure-sensitive adhesive composition for masking tape - Google Patents

Abstract

PURPOSE:To provide the title composition which has sufficient tack at ordinary temperature, lowly decreases in tack at high temperatures, does not remain when released and is good in the linearity of a coating film. CONSTITUTION:An acrylic pressure-sensitive adhesive composition for a masking tape comprising a polymer obtained by copolymerizing a monomer mixture consisting mainly of an alkyl (meth)acrylate with a 4 C or higher alkyl, wherein the tack of a pressure-sensitive adhesive tape or sheet, prepared by applying to composition to a support, to a SUS304 steel sheet is 35gf/25mm or above at 90 deg.C, and the ball number as measured by the rolling ball method is 10 or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bumper for automobiles,
The present invention relates to an acrylic pressure-sensitive adhesive composition for a masking tape used for coating outer panels and the like.

[0002]

2. Description of the Related Art Various masking tapes are used for coating automobiles and the like, but in recent years, high-quality heat-resistant masking tapes that can be used for baking and drying coating have been demanded. As specific required performance, for example,
(1) It has sufficient adhesive strength at room temperature so that it can be applied in a short time in the coating line, (2) it does not peel off during baking and drying at high temperature, and (3) tape after baking and drying. The adhesive does not remain on the peeling surface, (4) the coating line of the masking part can be clearly seen, and (5) it is non-staining and does not discolor the coating on the tape sticking surface. .

By the way, conventionally, rubber-based pressure-sensitive adhesives centering on natural rubber have been mainly used for coating masking tapes. The rubber-based pressure-sensitive adhesive is used after being crosslinked with a crosslinking agent such as a phenol resin or a sulfur compound, if necessary. When a masking tape using this rubber-based pressure-sensitive adhesive is attached to a coated surface and sprayed with a coating material, the coating material may be contaminated or a sticking mark may be generated depending on the type of the coating material.

On the other hand, a masking tape using an acrylic pressure-sensitive adhesive has the advantages that it is non-staining and has few traces of sticking. However, the acrylic pressure-sensitive adhesive is
Adhesiveness at room temperature or relatively low temperature is good, but at high temperature, the adhesive force drops sharply and peels off with a slight force. Therefore, when the acrylic pressure-sensitive adhesive tape is used as a coating masking tape, there is a problem that the adhesiveness is lowered and the tape is peeled off from the adherend when the temperature is increased during baking and drying.

Polymers used for acrylic pressure-sensitive adhesives contain, in addition to the main acrylic monomer, functional monomers and various comonomers as monomer components in order to improve cohesiveness and tackiness. Further, in order to improve the internal cohesive force of the acrylic pressure-sensitive adhesive, a functional monomer serving as a cross-linking point is used as a comonomer and cross-linking is performed by the cross-linking agent. Therefore, if the proportion of the functional monomer used is increased in order to improve the adhesive strength of the acrylic pressure-sensitive adhesive tape at high temperatures, the adhesiveness at room temperature will decrease and the adhesive will remain when the tape is peeled off. Further, if the amount of the crosslinking agent is increased in order to prevent the adhesive from remaining, there is a problem such that the linearity of the coating film at the masking portion is deteriorated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to have a sufficient adhesive force at room temperature, to reduce the adhesive force at a high temperature little, and to prevent the adhesive from remaining, and to improve the lineability of the coating film. Another object of the present invention is to provide an acrylic pressure-sensitive adhesive composition for masking tape.

As a result of intensive studies to overcome the above-mentioned problems of the prior art, the present inventors have found that a monomer mixture containing a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms as a main component is used as a main component. It has been found that a pressure-sensitive adhesive composition having a specific physical property containing a polymer obtained by polymerization can achieve the above-mentioned object, and based on this finding, the present invention has been completed.

[0008]

Thus, according to the present invention, a polymer containing a polymer obtained by copolymerizing a monomer mixture containing a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms as a main component is included. A pressure-sensitive adhesive composition, wherein the adhesive tape or sheet obtained by coating the composition on a support has an adhesive force at 90 ° C. of 25 gf / 25 mm or more and a ball number of 10 or more by a ball rolling method. An acrylic pressure-sensitive adhesive composition for a masking tape is provided.

The present invention will be described in detail below. The acrylic pressure-sensitive adhesive composition for a masking tape of the present invention has an adhesive strength (at 90 ° C.) of an adhesive tape (or sheet) obtained by coating the composition on a support at 90 ° C. of 25 gf / 25 mm or more. is necessary. 9
If the adhesive strength at 0 ° C. is less than 25 gf / 25 mm, the adhesive tape may float (lifting of the tape edge) during hot air drying or may be easily peeled off. The adhesive strength at 90 ° C. is preferably 35 gf / 25 mm or more.

The acrylic pressure-sensitive adhesive composition for a masking tape according to the present invention has a ball number according to the ball rolling method (JIS Z 0237: inclined ball tack) of the adhesive tape coated with the composition. Is required to be 10 or more. When the ball number is less than 10,
Sufficient tack cannot be obtained at room temperature, and the adhesive strength at room temperature decreases.

In the present invention, as the acrylic polymer, a monomer mixture having the following composition (total 100% by weight)
A polymer obtained by copolymerizing the above can be used. Monomer composition (A) Acrylic acid alkyl ester having a C4-12 alkyl group 1.5 to 90% by weight (B) Methacrylic acid alkyl ester having a C4-18 alkyl group 0 to 98% by weight (C ) N-vinylpyrrolidone 0-20% by weight (D) Acrylamide 0-10% by weight (E) Unsaturated carboxylic acid 0.5-5% by weight (F) Other copolymerizable monomer 0-10% by weight

Hereinafter, each monomer component will be described. (A) Acrylic Acid Alkyl Ester Having an Alkyl Group Having 4 to 12 Carbons The acrylic acid alkyl ester having an alkyl group having 4 to 12 carbons is a component that imparts tack and tackiness at room temperature. Specific examples include, for example, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate (2EHA), heptyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, decyl acrylate, lauryl acrylate, and the like. A mixture etc. are mentioned.

The ratio of the monomer component (A) used is 1.5.
˜90 wt%, preferably 10-90 wt%.
If it is less than 1.5% by weight, sufficient tack cannot be obtained at room temperature, and conversely, if it exceeds 90% by weight, the adhesive strength at 90 ° C. to the SUS304 plate decreases.

(B) Methacrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms Specific examples of the methacrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms include, for example, butyl methacrylate, amyl methacrylate, 2- Ethylhexyl methacrylate, heptyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, decyl methacrylate, lauryl methacrylate (LMA), tridecyl methacrylate, isotetradecyl methacrylate, cetyl methacrylate, stearyl methacrylate, these A mixture etc. are mentioned.

The proportion of the monomer component (B) used is 0-9.
8% by weight. If this ratio exceeds 98% by weight, sufficient tack cannot be obtained at room temperature. A preferable usage ratio of the monomer component (B) is 10% by weight or more, whereby a good balance between tack at room temperature and adhesive strength at 90 ° C. can be obtained.

(C) N-Vinylpyrrolidone N-Vinylpyrrolidone (NVP) is a component that improves the adhesive strength at high temperatures. The monomer component (C) need not be used, but when it is used, it is used up to 20% by weight. If it exceeds 20% by weight, the tack at room temperature decreases.

(D) Acrylamide Acrylamide (AAm) is a component that improves the adhesive strength at high temperatures. The component (D) includes methacrylamide, n, n-dimethylacrylamide, n-methylolacrylamide, isopropylacrylamide and the like in addition to acrylamide. The monomer component (D) is
It is not necessary to use it, but when it is used, it is up to 10% by weight. If it exceeds 10% by weight, tack at room temperature is lowered, and the adhesive tends to remain after being heated to a high temperature.

(E) Unsaturated Carboxylic Acid The unsaturated carboxylic acid is a component that crosslinks the pressure-sensitive adhesive composition to impart cohesiveness and solvent resistance. As a specific example,
Examples thereof include acrylic acid (AA), methacrylic acid, itaconic acid, maleic acid, maleic anhydride, crotonic acid and fumaric acid.

The usage ratio of the monomer component (E) is 0.5.
~ 5% by weight. If it is less than 0.5% by weight, sufficient cohesiveness and solvent resistance cannot be obtained, and conversely, if it exceeds 5% by weight, tack at room temperature is lowered, and after heating to high temperature, the adhesive It tends to remain.

(F) Other Copolymerizable Monomer The other copolymerizable monomer is a component that modifies the characteristics of the pressure-sensitive adhesive composition at room temperature or high temperature. Specific examples thereof include (meth) acrylic acid alkyl esters having 1 to 3 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. In addition, vinyl acetate (VAc),
Vinyl propionate, acrylonitrile, styrene, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxy Examples include propyl (meth) acrylate and glycidyl (meth) acrylate.

These monomer mixtures are prepared by the solution polymerization method,
Copolymerization can be carried out by a conventionally known method such as an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, etc. However, the solution polymerization method is preferable in that it has less contamination and is easy to polymerize. Examples of the solvent used for the polymerization include toluene, hexane, heptane, ethyl acetate, methyl acetate, acetone, methyl ethyl ketone, methanol, t-butyl alcohol and the like.

Examples of the polymerization initiator include peroxide initiators such as benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, azobisisobutyronitrile, azobiscyanovaleric acid, and azo. Examples thereof include azo-based initiators such as biscyanopentanoic acid and azobis-2-cyanopropane.

Polymerization modifiers can be used to adjust the molecular weight. Examples of the polymerization regulator include thioglycolic acid, 2-ethylhexyl thioglycolate,
Dodecyl mercaptan, octyl mercaptan, lauryl mercaptan, 2-mercaptoethanol, carbon tetrachloride and the like can be mentioned.

In the present invention, as the acrylic polymer, those obtained by copolymerizing the above-mentioned monomer components (A) to (F) at one time can be used. However, these monomer components are divided and polymerized. The obtained polymer can be blended and used after the polymerization. That is, a mixture of a polymer (a) obtained by copolymerizing a monomer mixture having the following composition [I] and a polymer (b) obtained by copolymerizing a monomer mixture having the following composition [II] can be used.

Monomer composition [I] (A) Alkyl acrylate having an alkyl group having 4 to 12 carbon atoms 70 to 99.5% by weight (E) Unsaturated carboxylic acid 0.5 to 5% by weight (F) Others Copolymerizable monomer of 0 to 29.5% by weight Monomer composition [II] (B) Methacrylic acid alkyl ester having alkyl group having 4 to 18 carbon atoms 70 to 100% by weight (C) N-vinylpyrrolidone 0 to 20% by weight % (D) Acrylamide 0 to 10% by weight (E) Unsaturated carboxylic acid 0 to 5% by weight (F) Other copolymerizable monomer 0 to 30% by weight

The mixing ratio (a: b) of the polymer (a) and the polymer (b) is usually within the range of 95: 5 to 50:50. If the proportion of the polymer (a) exceeds 95% by weight, the adhesive strength at high temperature cannot be exhibited, and conversely 50% by weight.
When it is less than 1, the tack at room temperature is lowered, and thus both are not preferable. In addition, by using such a blend, it is possible to obtain a desired balance between tackiness and adhesive strength at high temperature by adjusting the use ratio of each monomer component or the mixing ratio of polymers.

When the acrylic pressure-sensitive adhesive composition is blended with a polymer having a different composition, they are not compatible with each other and the solution is easily separated into layers, but when the molecular weight of the polymer is small, the layers are not separated. The average molecular weight of the polymer (a) is 3
The range of 0 to 1.2 million is preferable. When the average molecular weight of the polymer (a) exceeds 1.2 million, gelation is likely to occur during polymerization. The polymer (b) preferably has an average molecular weight of 100,000 or less because the solution tends to separate into layers when mixed with the polymer (a) when the polymer (b) has a high molecular weight. Not expressed, also
Since it may cause contamination, it is preferably at least 5,000 or more.

The layer separation phenomenon as described above is not a serious problem for a short period of time, and when applied to a tape or sheet substrate, the pressure-sensitive adhesive is usually crosslinked. Therefore, the change in tape characteristics over time does not pose a problem. However, when the solution is stored for a long period of time, the layers may be separated. In such a case, if one polymer is polymerized in advance and another monomer component is added in the presence of this polymer and polymerized, the solution containing the pressure-sensitive adhesive does not cause layer separation even after long-term aging.

That is, the monomer mixture of the composition [II] is copolymerized in the presence of the polymer (a) obtained by copolymerizing the monomer mixture of the composition [I], or the monomer mixture of the composition [II] is By copolymerizing the monomer mixture having the above composition [I] in the presence of the polymer (b) obtained by copolymerizing the monomer mixture, layer separation can be prevented over time. The reason for this is presumed to be that graft polymerization partially occurs during the second-stage polymerization and the resulting graft product acts as a compatibilizer. In this case, as in the polymer blend, the use ratio (I: I) of the monomer composition [I] and the monomer composition [II] is used.
I) is preferably within the range of 95: 5 to 50:50.

Since the acrylic polymer obtained as described above has a low cohesive force, a crosslinking agent is usually added. As the cross-linking agent, for example, polyisocyanate-based,
Known cross-linking agents such as epoxy resin type, melamine resin type and metal type are used. Further, if desired, a filler, a coloring agent, a softening agent and the like may be added within a range that does not deteriorate the adhesive property.

The support (base material) to which the pressure-sensitive adhesive composition of the present invention is applied is, for example, Japanese paper, crepe paper, cloth,
A film of polyester, polypropylene, vinyl chloride, polyethylene, or the like, or a composite substrate of these is used.

As described above, by copolymerizing a monomer component that imparts tackiness at room temperature and a monomer component that imparts tackiness at high temperature, an acrylic-based feel that exhibits tackiness in a wide range from room temperature to high temperature. A pressure-sensitive adhesive composition is obtained.

[0033]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The method of measuring the physical properties of the adhesive is as follows. <Adhesiveness> 180 ° peeling adhesion to a stainless steel plate (SUS304) according to JIS Z 0237-8 using a sample obtained by coating an acrylic pressure-sensitive adhesive composition on a soft vinyl chloride sheet with a dry thickness of 30 μm. Force (gf / 25 mm) was determined at 23 ° C.

<Adhesiveness at 90 ° C.> JIS Z 0
It is measured according to 8 of 237, but it is attached to a SUS304 steel plate at 23 ° C., and after pressure bonding it is left at 90 ° C. for 20 minutes and peeled off in an atmosphere of 90 ° C. (gf / 25 m
m) was calculated.

<Ball tack> Measured by the ball rolling method of JIS Z 0237 12, and indicated by a ball number.

<Adhesive Residue Test> Commercially available white paint is spray-painted on a polypropylene plate (PP plate) and the temperature is 120 ° C.
After drying for 20 minutes (thickness 40 μm), an adhesive tape was applied, and after heating at 120 ° C. for 20 minutes, the tape was immediately peeled off and the case of peeling after cooling was visually observed for the presence of an adhesive, The following three grades were used for the evaluation.

◯: No residue, Δ: slightly residual, X: Remaining on the entire surface of the tape.

[Examples 1 to 6 and Comparative Examples 1 to 5] 100 parts by weight of a monomer mixture having the number shown in Table 1 in a reactor equipped with a stirrer, a cooling pipe, a thermometer, a nitrogen introducing pipe, and a dropping funnel. And 150 parts by weight of ethyl acetate were added, and the temperature was raised to 60 ° C. while enclosing nitrogen gas. After that, the temperature was maintained at 60 ° C., and azobisisobutyronitrile as an initiator was added as an initiator.
1 part by weight was added and polymerization was carried out for 8 hours. In order to complete the polymerization, the temperature was further raised to 80 ° C. and kept for 2 hours.

2 parts by weight of an isocyanate crosslinking agent was added to the obtained reaction mixture to obtain a pressure sensitive adhesive solution. This was applied to a soft vinyl chloride sheet and dried at 120 ° C. for 5 minutes to obtain a pressure sensitive adhesive sheet (dry thickness of adhesive layer 30
μm). The results of measuring the adhesive properties of these sheets are shown in Table 1. The adhesive strength at 90 ° C is 25g
For the adhesive tape with f / 25 mm or less, the tape edge was lifted by dry hot air during the residual test of the pressure-sensitive adhesive.

[0041]

[Table 1]

[Examples 7 to 14] Monomer composition [I] (A, B) and monomer composition [II] (a, b, c, d) shown in Table 2 were used under the same equipment and conditions as above. Polymerized. Table 3 shows each of the obtained polymers (A to B and a to d).
The mixture shown in (1) and (2) were mixed at a mixing ratio, and 3 parts by weight of an isocyanate compound was added as a crosslinking agent to obtain a pressure-sensitive adhesive solution. This was applied to a soft vinyl chloride sheet in the same manner as above to prepare a pressure-sensitive adhesive sheet, and the same evaluation was performed. The results are shown in Table 3. As a result of the pressure-sensitive adhesive residual test, no pressure-sensitive adhesive remained. Further, these pressure-sensitive adhesive solutions gelled on the third day, but no layer separation of the pressure-sensitive adhesive was observed.

[0043]

[Table 2]

[0044]

[Table 3]

[Examples 15 to 16 and Comparative Examples 6 to 9] The mixing ratios of the polymer A and the polymer a obtained above were changed as shown in Table 4, and 3 parts by weight of an isocyanate crosslinking agent was added. A pressure sensitive adhesive solution was obtained. This was applied to a soft vinyl chloride sheet in the same manner as above to prepare a pressure-sensitive adhesive sheet, and the same evaluation was performed. The results are shown in Table 4.

[0046]

[Table 4]

Example 17 The monomer composition a was prepared by polymerizing 70 parts by weight of the monomer composition A in the above example.
30 parts by weight and polymerization initiator (benzoyl peroxide)
Polymerization was carried out by adding 0.03 part by weight. 3 parts by weight of an isocyanate-based crosslinking agent was added to the obtained polymer to obtain a pressure sensitive adhesive solution. A pressure-sensitive adhesive sheet of soft vinyl chloride was obtained in the same manner as above, and the same evaluation was performed. The results are shown in Table 5.
Shown in. The pressure-sensitive adhesive solution containing the cross-linking agent is 3
Although gelled on the day, layers not added did not undergo layer separation even after 1 month.

Example 18 In Example 17, the polymerization order was reversed. That is, after 30 parts by weight of the monomer composition a was polymerized, 70 parts by weight of the monomer composition A and 0.03 part by weight of a polymerization initiator (benzoyl peroxide) were added for polymerization. 3 parts by weight of an isocyanate-based crosslinking agent was added to the obtained polymer to obtain a pressure sensitive adhesive solution. In the same manner as above, to obtain a pressure-sensitive adhesive sheet of soft vinyl chloride,
Similar evaluation was performed. The results are shown in Table 5. The pressure-sensitive adhesive solution containing the crosslinking agent gelled on the third day,
The layers not added did not undergo layer separation even after 1 month.

[0049]

[Table 5]

[0050]

According to the acrylic pressure-sensitive adhesive composition of the present invention, the decrease in the adhesive strength of the conventional masking tape at high temperature is improved, and the adhesiveness is maintained even at high temperature.
It is possible to provide a masking tape that does not cause floating. Further, by appropriately combining the monomer composition of the acrylic pressure-sensitive adhesive composition, the functional group and the crosslinking agent, it is possible to provide a masking tape which prevents the adhesive from remaining and has excellent lineability.

Continued front page    (72) Inventor Masao Haibara             2-4 2-9, Kudanminami, Chiyoda-ku, Tokyo             Inside Chiban Co., Ltd.

Claims (7)

[Claims] 1. A pressure-sensitive adhesive composition containing a polymer obtained by copolymerizing a monomer mixture containing a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms as a main component. 90 ° C for an adhesive tape or sheet coated with an object on a SUS304 steel plate
The adhesive pressure-sensitive adhesive composition for masking tape is characterized by having an adhesive strength of 25 gf / 25 mm or more and a ball number of 10 or more by a ball rolling method. 2. The acrylic pressure-sensitive adhesive composition for a masking tape according to claim 1, wherein the polymer is a polymer obtained by copolymerizing a monomer mixture having the following composition. (A) Acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms 1.5 to 90% by weight (B) Methacrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms 0 to 98% by weight (C) N -Vinylpyrrolidone 0 to 20% by weight (D) acrylamide 0 to 10% by weight (E) unsaturated carboxylic acid 0.5 to 5% by weight (F) other copolymerizable monomer 0 to 10% by weight 3. A mixture of a polymer (a) obtained by copolymerizing a monomer mixture having the following composition [I] with a polymer (b) obtained by copolymerizing a monomer mixture having the following composition [II]. The acrylic pressure-sensitive adhesive composition for a masking tape according to claim 1. Monomer composition [I] (A) Acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms 70 to 99.5% by weight (E) Unsaturated carboxylic acid 0.5 to 5% by weight (F) Other copolymerization Monomer 0 to 29.5% by weight Monomer composition [II] (B) Methacrylic acid alkyl ester having alkyl group having 4 to 18 carbon atoms 70 to 100% by weight (C) N-vinylpyrrolidone 0 to 20% by weight (D ) Acrylamide 0 to 10% by weight (E) Unsaturated carboxylic acid 0 to 5% by weight (F) Other copolymerizable monomer 0 to 30% by weight 4. The acrylic pressure-sensitive adhesive for masking tape according to claim 3, wherein the mixing ratio (a: b) of the polymer (a) and the polymer (b) is within the range of 95: 5 to 50:50. Composition. 5. A polymer obtained by copolymerizing a monomer mixture of the following composition [II] in the presence of the polymer (a) obtained by copolymerizing the monomer mixture of the following composition [I], or In the presence of a polymer (b) obtained by copolymerizing a monomer mixture having the following composition [II],
The acrylic pressure-sensitive adhesive composition for a masking tape according to claim 1, which is a polymer obtained by copolymerizing a monomer mixture having the following composition [I]. Monomer composition [I] (A) Acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms 70 to 99.5% by weight (E) Unsaturated carboxylic acid 0.5 to 5% by weight (F) Other copolymerization Monomer 0 to 29.5% by weight Monomer composition [II] (B) Methacrylic acid alkyl ester having alkyl group having 4 to 18 carbon atoms 70 to 100% by weight (C) N-vinylpyrrolidone 0 to 20% by weight (D ) Acrylamide 0 to 10% by weight (E) Unsaturated carboxylic acid 0 to 5% by weight (F) Other copolymerizable monomer 0 to 30% by weight 6. A monomer composition [I] and a monomer composition [I
I] is used in a ratio (I: II) of 95: 5 to 50:50.
The acrylic pressure-sensitive adhesive composition for a masking tape according to claim 5, which is within the range. 7. The acrylic pressure-sensitive adhesive composition for a masking tape according to claim 1, which contains the polymer and a crosslinking agent.