JP2002053832A - Repeelable adhesive composition and protecting film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repeelable adhesive composition that has no repelling problem because of containing no silicone component, has moderate balance between the adhesion and the repeelable property, and less alteration in the adhesion and the peeling properties caused by the temperature change. SOLUTION: This repeelable adhesive composition includes (A) an acrylate- vinyl acetate copolymer constituted with (a) 80-99.0 wt.% of an (meth)acrylic alkyl ester bearing a 1-9C alkyl group, (b) 0.5-20.0 wt.% of vinyl acetate monomer, (c) 0.1-5.0 wt.% of copolymerizable unsaturated monomers bearing hydroxyl and/or carboxyl groups and (B) one or more kinds of reactive mono-functional isocyanate containing a long chain of >=10 carbon atoms wherein the reactive monofunctional isocyanate (B) is added in an amount of 0.5-16.5 pts.wt. per 100 pts.wt. of the acrylate-vinyl acetate copolymer (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a removable pressure-sensitive adhesive composition and a protective film using the same.

[0002]

2. Description of the Related Art Generally, as a protective film for an adhesive tape or the like, a silicone-treated release paper or a release film obtained by applying release silicone to paper or a plastic film is generally used. Or there are applications where release films are not suitable. For example, in the automobile manufacturing process of attaching metal or plastic parts to the body of an automobile before painting, an adhesive tape such as a quasi-structured acrylic tape has metal or plastic parts on one side and a release paper or film on the other side. Components with tapes are used. Such a taped component is obtained by removing a release paper or a release film from the tape and affixing it to an automobile body. At this time, if the release paper or the release film has been silicone-treated, the release paper or the release film or the silicone on the release film may directly contact the body of the automobile, or may be indirectly in contact with the worker's gloves. When silicone adheres to the body, cissing of the paint is generated. Therefore, it is common that release paper and release film which have been subjected to silicone treatment cannot be used, and in such a case, a polyolefin-based non-silicone protective film is used. However, the polyolefin-based protective film has no tackiness like the silicone-treated release paper or release film. On the other hand, the pressure-sensitive adhesive of the pressure-sensitive adhesive tape on the protected side generally has a large change in adhesive strength depending on the environmental temperature. In particular, when a non-adhesive protective film such as the above-mentioned polyolefin-based protective film is used, the adhesive strength with the adhesive tape is reduced at a low temperature in winter, and the protective film is unintentionally peeled off and parts are detached. Therefore, there arises a problem that parts cannot be held or transported.

[0003] On the other hand, acrylic-based and urethane-based removable protective films and the like are also commercially available, but they are generally used mainly for protecting the surface of non-adhesive materials such as metal, wood, and plastic. A removable pressure-sensitive adhesive composition usable as such a protective film is disclosed in JP-A-9-2089.
No. 10 discloses this. According to this publication, the disclosed removable adhesive composition can be used as a protective film for electronic devices, and specifically, 100 parts by weight of the following components (a) to (d): (A) alkyl acrylates having 1 to 9 carbon atoms in the alkyl group, 65 to 9
8.4% by weight, (b) a copolymerizable unsaturated monomer containing a hydroxyl group and / or a carboxyl group, from 0.5 to 10
Acrylate containing (c) an alkyl (meth) acrylate having 16 to 22 carbon atoms in an alkyl group, 1 to 20% by weight, and (d) a reactive emulsifier, 0.1 to 5% by weight. It is obtained by adding 0.1 to 5 parts by weight of a crosslinking agent to the system copolymer. The reactive emulsifier is included for the purpose of preventing the pressure-sensitive adhesive from being charged, and the surface resistance of the pressure-sensitive adhesive is reduced by such an emulsifier. However, when the disclosed removable adhesive composition is used as a protective film for an adhesive tape such as an acrylic tape for a substructure, the amide group, ammonium group, and amino group derived from the reactive emulsifier may be used. When it reacts with the epoxy resin in the structural acrylic tape, it may not exhibit relatively good releasability. Further, there is a high possibility that the hydroxyl group contained in the emulsifier hydrophilizes the pressure-sensitive adhesive and increases the peeling force in a high-humidity environment. Further, the emulsifier may contaminate the adherend. In the pressure-sensitive adhesive, a crosslinker is used in addition to copolymerizing an alkyl (meth) acrylate having 16 to 22 carbon atoms in the alkyl group in order to obtain a balance between the tackiness and the releasability. However, the balance between the adhesiveness and the releasability greatly changes depending on the amount of the crosslinking agent, and it is difficult to obtain the desired releasability and adhesiveness.

[0004]

As described above, currently used protective films for adhesive materials such as adhesive tapes contain silicone and / or do not have adhesiveness. There is a problem of contamination by silicone and a problem of a large change in the peeling force of the protective film due to a change in environmental temperature. Further, the protective film using the removable adhesive composition is intended to protect the surface of the non-adhesive material, a single-sided adhesive film tape, an adhesive transfer tape, a double-sided adhesive tape, a double-sided adhesive foam tape and a double-sided adhesive foam tape There is currently no attempt at protecting adhesive materials such as acrylic tape for adhesive semi-structure. Thus, a protective film having both good adhesiveness to the tape and excellent releasability is desired. Accordingly, an object of the present invention is to contain no silicone, so that there is no problem of repelling of the coating, and there is a proper balance between the adhesiveness and the removability, and the adhesiveness and the re-adhesion due to a change in the environmental temperature are eliminated. An object of the present invention is to provide a removable pressure-sensitive adhesive composition having a small change in releasability and a protective film using the same.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. According to the present invention,
(A) alkyl (meth) acrylate having 1 to 9 carbon atoms in the alkyl group, 80 to 99.0% by weight, (b) vinyl acetate monomer, 0.5 to 20.0% by weight, (c) hydroxyl group And / or a carboxyl group-containing copolymerizable unsaturated monomer, an acrylic / vinyl acetate copolymer (A) composed of a monomer component containing 0.1 to 5.0% by weight, and having 10 or more carbon atoms 1 having an alkyl group of
At least one reactive monofunctional isocyanate (B),
The removable pressure-sensitive adhesive composition, wherein the reactive monofunctional isocyanate (B) is added in an amount of 0.5 to 16.5 parts by weight based on 100 parts by weight of the acrylic / vinyl acetate copolymer (A). Things are provided. Further, according to the present invention, the removable pressure-sensitive adhesive composition is applied to a substrate, and the reactive monofunctional isocyanate (B) is subjected to an addition reaction to the acryl / vinyl acetate copolymer (A). A protective film is provided. The removable adhesive composition and the protective film do not contain silicone. For this reason, there is no problem of repelling of the coating, and there is a proper balance between the adhesiveness and the removability, and the change in the adhesiveness and the removability due to the change in the environmental temperature is small. For this reason, the adhesive strength with the adhesive tape to be stuck is kept constant from a low temperature in winter to a high temperature in summer, so that peeling is easy and there is no hindrance in holding and transporting parts.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The removable pressure-sensitive adhesive composition of the present invention contains an acrylic / vinyl acetate copolymer (A). This copolymer comprises (a) an alkyl (meth) acrylate having an alkyl group having 1 to 9 carbon atoms, (b) a vinyl acetate monomer, and (c) a copolymerizable unsaturated monomer having a hydroxyl group and / or a carboxyl group. It is composed of a monomer component containing a monomer.

The alkyl (meth) acrylate having 1 to 9 carbon atoms in the alkyl group (component (a)) is an acrylic
A main monomer component contained in a vinyl acetate copolymer, and in combination with a vinyl acetate monomer (component (b)), is adhesive to an adhesive composition at an ambient temperature (for example, a temperature of 5 to 55 ° C). Has the function of giving Further, the component (b) has a function of giving a cohesive force to the pressure-sensitive adhesive composition. Specific examples of component (a) include methyl acrylate and methacrylate, ethyl acrylate and methacrylate, n-butyl acrylate and methacrylate, isobutyl acrylate and methacrylate, isoamyl acrylate and methacrylate, 2-ethylhexyl acrylate and methacrylate, isooctyl acrylate and Examples include methacrylate, n-octyl acrylate and methacrylate and isononyl acrylate and methacrylate. Components (a) and (b) are each 80
-99% by weight and 0.5-20.0% by weight, preferably 90-99% by weight and 0.5-10% by weight. If the component (a) is below the above-mentioned amount, that is, if the component (b) is above the above-mentioned amount, the tackiness may not be sufficient.

In the removable pressure-sensitive adhesive composition of the present invention,
Removability is obtained by the reaction between the acrylic / vinyl acetate copolymer (A) and the reactive monofunctional isocyanate (B). When the isocyanate-based crosslinking agent (C) is contained, the cohesive force of the pressure-sensitive adhesive composition is improved by the reaction between the copolymer (A) and the crosslinking agent (C).
Such a reaction is carried out by reacting a hydroxyl group and / or a carboxyl group in the copolymerizable unsaturated monomer (component (c)) with an isocyanate group in the reactive monofunctional isocyanate (B) and optionally contained isocyanate-based crosslinking agent. During the addition reaction. For this reason, component (c) should be in an amount sufficient to carry out the reaction with the reactive monofunctional isocyanate (B) and the crosslinking agent (C). In the removable pressure-sensitive adhesive composition of the present invention, releasability is obtained by a long-chain alkyl group having 10 or more carbon atoms having low surface energy in the reactive monofunctional isocyanate (B). If this amount is too small, the reactive monofunctional isocyanate (B)
Is not sufficiently obtained due to the addition of the compound. On the other hand, if the amount is too large, unreacted hydroxyl groups and / or carboxyl groups remain. In this case, too, the peelability is impaired, especially in an environment with high humidity. The peel force increases. Thus, the amount of component (c) is between 0.1 and 5.0% by weight.

Examples of the component (c) include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate,
Acrylic acid, methacrylic acid, maleic acid, crotonic acid,
β-carboxyethyl acrylate and the like.

The acrylic-vinyl acetate copolymer (A) contained in the pressure-sensitive adhesive composition of the present invention has a weight average molecular weight of 50
000 to 1,200,000, preferably 600,
000 to 1,000,000. When the weight average molecular weight of the copolymer (A) is less than 500,000, the cohesive force of the pressure-sensitive adhesive composition is insufficient, and when it exceeds 1,200,000, the viscosity of the solution of the composition becomes too high, This is because coatability may be poor.

As described above, the reactive monofunctional isocyanate (B) imparts releasability to the pressure-sensitive adhesive composition by reacting with a hydroxyl group and / or a carboxyl group contained in the acrylic / vinyl acetate copolymer. I do. The reactive monofunctional isocyanate (B) has a low surface energy of 1 carbon atom.
It has 0 or more long-chain alkyl groups. Specific examples include C ₁₀ -C ₂₀ alkyl groups, preferably dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, nonadecyl or eicosyl. Isocyanate (B) is, for example, C ₁₀ -C ₂₀
And includes, for example, octadecyl isocyanate and the like. In the removable pressure-sensitive adhesive composition of the present invention, the releasability can be easily controlled by controlling the amount of the reactive monofunctional isocyanate (B). The amount of the isocyanate (B) to be added is 0.5 to 16.5 parts by weight per 100 parts by weight of the acrylic / vinyl acetate copolymer. When the amount of the isocyanate (B) is less than 0.5 part by weight, the releasability becomes poor, and 16.5.
When the amount is larger than the weight part, there is a possibility that contamination on an adherend such as an acrylic adhesive tape may occur.

The pressure-sensitive adhesive composition of the present invention comprises an isocyanate-based crosslinking agent (C) for improving the cohesive strength of the pressure-sensitive adhesive composition.
May be included. Such a cross-linking agent is an isocyanate having two or more functionalities, and has a hydroxyl group and / or a hydroxyl group in the monomer component of the component (c) present in the acryl / vinyl acetate copolymer.
Alternatively, it reacts with a carboxyl group to form a crosslink. When a crosslinking agent is included, it is included in an amount of 1.5 to 15.0 parts by weight per 100 parts by weight of the acrylic vinyl acetate copolymer. If the amount is more than 16.5 parts by weight, the adhesiveness may be excessively reduced. Specific examples of the isocyanate-based crosslinking agent (C) include aromatic diisocyanates such as tolylene diisocyanate and xylene diisocyanate, aliphatic or alicyclic diisocyanate compounds such as hexamethylene diisocyanate and isophorone diisocyanate, and trimethylolpropane and the like. An adduct with a compound containing a hydroxyl group may be mentioned.

The pressure-sensitive adhesive composition of the present invention can be produced as follows. First, an acrylic / vinyl acetate copolymer is obtained by copolymerizing monomers of components (a), (b) and (c). The copolymer can be formed by radiation polymerization using an ultraviolet ray, an electron beam (EB), or the like. The polymer is solution-polymerized in the presence of a predetermined polymerization initiator,
It can be produced by a conventional method such as suspension polymerization, emulsion polymerization, bulk polymerization and the like. For example, a copolymer is obtained by radical polymerization using, as the polymerization initiator, an organic peroxide such as benzoyl peroxide or lauryl peroxide, or an azo polymerization initiator such as azobisisobutyronitrile. Is obtained. Commercially available acrylic / vinyl acetate copolymers include SK manufactured by Soken Chemical Co., Ltd.
Dyne 1495 can be used.

The pressure-sensitive adhesive composition of the present invention can be obtained by adding a predetermined amount of a reactive monofunctional isocyanate to the above copolymer. If desired, a bifunctional or higher isocyanate crosslinking agent can be added. Commercially available reactive monofunctional isocyanates include Millionate O (O) manufactured by Hodogaya Chemical Co., Ltd. Further, as a commercially available isocyanate-based crosslinking agent, a curing agent L-45 manufactured by Soken Chemical Co., Ltd. can be exemplified.

[0015] The pressure-sensitive adhesive composition of the present invention is applied to a base material such as paper, plastic, woven fabric or non-woven fabric, and further applied to a substrate.
By heating at ~ 120 ° C, a protective film can be formed. Upon heating, the reactive monofunctional isocyanate (B) and the isocyanate-based crosslinking agent (C) optionally contained cause an addition reaction with a hydroxyl group and / or a carboxyl group in the copolymer (A). The thickness when forming the protective film is not particularly limited, but usually 10 to
30 μm. When the pressure-sensitive adhesive composition of the present invention is applied to a plastic substrate such as a polyester film, a corona treatment may be performed to improve the adhesion between the substrate and the pressure-sensitive adhesive composition. The obtained protective film can be particularly preferably used as a protective film for a single-sided adhesive film tape, an adhesive transfer tape, a double-sided adhesive tape, a double-sided adhesive foam tape, and a double-sided adhesive semi-structure acrylic tape.

The pressure-sensitive adhesive composition of the present invention comprises, in addition to the above components, a heat aging inhibitor, an antiozonant, a softener, a plasticizer, a lubricant, a coloring agent, an antistatic agent, an antibacterial agent, an ultraviolet absorber, Various additives such as a flame retardant can be mixed.

[0017]

EXAMPLE 1 A solution of an acrylic / vinyl acetate copolymer (A) dissolved in a solvent of toluene / vinyl acetate (Solken Chemical Co., Ltd.
K Dyne 1495: solid content 30% by weight), 100 g, octadecyl isocyanate (Millionate O manufactured by Hodogaya Chemical Co., Ltd .: 100% solid content) as a reactive monofunctional isocyanate (B) having a low surface energy group,
0.25 g, isocyanate-based cross-linking agent (C) (curing agent L-45 manufactured by Soken Chemical Co., Ltd .: solid content: 45% by weight),
3.0 g was stirred and mixed to produce a pressure-sensitive adhesive composition. This adhesive composition is dried so that the thickness after drying becomes 10 μm.
It was applied to a 5 μm thick polyester film. This film is heated to 100 ° C. for about 3 minutes to perform drying, addition reaction and crosslinking, and then a polyethylene release film is bonded thereto and left for 2 weeks in an atmosphere of 23 ° C./65% RH (relative humidity). Thus, a protective film was obtained.

Example 2 The pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the amount of the monofunctional isocyanate (B) in the pressure-sensitive adhesive composition component was 2.0 g and the amount of the isocyanate-based crosslinking agent was 3.5 g. And a protective film was obtained.

Comparative Example 1 Monofunctional isocyanate (B) as a component of the pressure-sensitive adhesive composition
A pressure-sensitive adhesive composition was produced with the same formulation as in Example 1 except that No. was added, and a protective film was obtained.

(1) Preparation of Peeling Sample The peeling film of the protective film (1) prepared in Examples 1 and 2 and Comparative Example 1 was peeled off, and an acrylic tape # 925 for double-sided adhesive semi-structure manufactured by Sumitomo 3M Ltd.
9 (2) was bonded so that air bubbles did not enter. Note that one end of the protective film (1) is stretched to 20 m.
m and pasted. Next, a strip having a width of 25 mm was cut in the vertical direction from the end of the stretched protective film (1) to obtain a test piece (see FIG. 1). (2) Peeling force measurement To measure the peeling force of the test piece, a width of 65 mm and a length of 7 mm were used.
A 5 mm and 0.8 mm thick steel plate (3) was placed such that the surface of the double-sided adhesive semi-structured acrylic tape # 9259 (2) was in contact with the steel plate, and affixed with a 2 kg roller. The laminate was left at a temperature of 5 ° C., 23 ° C. and 40 ° C. for one week, and then, at that temperature, the end of the protective film not bonded to the acrylic tape # 9259 (2) was grasped, and the JISZ0237 was pulled 90 °. The measurement was performed according to the peeling method (see FIG. 2). The protective film peeling force usually shows a high peak (B) at the start of peeling, and then shows a substantially uniform low peak ((C) (average value)) (see FIG. 3). The measurement results in this test are shown in Table 1 as the peak (B) at the start of peeling and the average value (C) of the peak excluding the peak at the start of peeling.

[0021]

[Table 1]

As is clear from the above results, the protective film obtained from the pressure-sensitive adhesive composition of the present invention has a peak at the start of peeling and a peak at the start of peeling at any temperature of 5 to 40 ° C. The difference between the average values of the excluded peaks is small,
Shows good peeling properties. In contrast, in Comparative Example 1,
The difference between the peak value at the start of peeling and the average value of the peaks is large. In particular, after leaving at 40 ° C. for one week, the peak value at the start of peeling exceeds 10 N, and it can be seen that the peak peeling force is greatly increased. .

[0023]

The pressure-sensitive adhesive composition of the present invention and the protective film using the same have both moderate adhesiveness and excellent peelability, and the resulting protective films are a single-sided adhesive film tape, a pressure-sensitive adhesive transfer tape. It can be suitably used as a protective film for a double-sided pressure-sensitive adhesive tape, a double-sided pressure-sensitive adhesive foam tape, and a double-sided pressure-sensitive acrylic tape for a semi-structure.

[Brief description of the drawings]

FIG. 1 is a perspective view of a test piece used in a test of an example.

FIG. 2 is a perspective view showing an operation of a 90 ° peeling method used in a test of an example.

FIG. 3 is a schematic diagram of a graph showing a general change in peeling force when a protective film is peeled off.

[Description of Signs] 1 ... Protective film 2 ... Acrylic tape for double-sided adhesive semi-structure 3 ... Steel plate A ... Tension direction B ... Peak value at the start of peeling C ... Average peak value excluding peak value at the start of peeling

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J004 AA10 AA14 AB01 CA06 CB01 CB02 CB04 CC02 CD08 EA05 FA04 GA01 4J040 DF041 DF051 EF071 EF181 EF291 EF301 GA05 GA07 JA09 JB02 JB09 KA16 LA06 MA02 MA10 NA16 PA42

Claims (4)

[Claims] 1. An alkyl (meth) acrylate having (a) an alkyl group having 1 to 9 carbon atoms, 80 to 99.0.
(B) a vinyl acetate monomer, 0.5 to 20.0% by weight, (c) a copolymerizable unsaturated monomer containing a hydroxyl group and / or a carboxyl group, 0.1 to 5.0% by weight. An acrylic-vinyl acetate copolymer (A) composed of a monomer component containing the same, and one or more reactive monofunctional isocyanates (B) having a long-chain alkyl group having 10 or more carbon atoms; Vinyl acetate copolymer (A) 100
A removable pressure-sensitive adhesive composition, wherein the reactive monofunctional isocyanate (B) is added in an amount of 0.5 to 16.5 parts by weight based on parts by weight. 2. 1.5 to 15.0 parts by weight of an isocyanate-based crosslinking agent (C) having a bifunctionality or more is added to 100 parts by weight of the acrylic / vinyl acetate copolymer (A). The removable pressure-sensitive adhesive composition according to claim 1. 3. The releasable pressure-sensitive adhesive composition according to claim 1, which is applied to a substrate and the reactive monofunctional isocyanate (B) is applied.
A protective film obtained by subjecting the above to the acrylic / vinyl acetate copolymer (A) to undergo an addition reaction. 4. The removable pressure-sensitive adhesive composition according to claim 2, which is applied to a substrate, and the reactive monofunctional isocyanate (B) is applied.
To the acrylic-vinyl acetate copolymer (A) and crosslinking the acrylic-vinyl acetate copolymer with the isocyanate-based crosslinking agent (C).