JP2011127052A - Pressure-sensitive adhesive composition for surface protecting sheet and surface protecting sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive composition for a surface protecting sheet which can produce the surface protecting sheet having high-speed peeling power lower than low-speed peeling power and excellent wettability. <P>SOLUTION: A component (A) including 3-40 wt.% of a (meth)acrylic acid alkylene oxide adduct and a component (B) including 60-97 wt.% of a polymerizable monomer except the (meth)acrylic acid alkylene oxide adduct are subjected to drop-wise polymerization where the component (A) and the component (B) begin to drop separately and simultaneously and the component (A) ends to drop with dropping time of 1/4 to 2/4 of that of the component (B) to obtain a (meth)acrylic copolymer having theoretical glass transition temperature of -50°C to 0°C. The (meth)acrylic copolymer is compounded with a crosslinking agent and is crosslinked to obtain the pressure-sensitive adhesive composition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive composition for a surface protective sheet. More specifically, the adhesive strength is high during low-speed peeling and the adhesive strength during high-speed peeling while having good wettability to an adherend. The present invention relates to a pressure-sensitive adhesive composition for a surface protective sheet and a surface protective sheet using the same.

  Conventionally, the re-peelable pressure-sensitive adhesive has been widely used for surface protective films, masking tapes, and the like, and natural rubber, synthetic rubber, and acrylic resin are used as its components. Among them, acrylic resins are often used because of excellent weather resistance, heat resistance, and ease of control of adhesive performance.

  Acrylic pressure-sensitive adhesive weakens the adhesive force and gives re-peelability. Therefore, the fluidity of the pressure-sensitive adhesive is suppressed by adding a component having a high glass transition temperature (Tg) or highly cross-linking with a cross-linking agent. A re-peelable pressure-sensitive adhesive is known (see Patent Document 1). However, the pressure-sensitive adhesive containing a component having a high Tg or highly crosslinked has a problem that the wetness due to the flow to the adherend becomes insufficient, and air remains to cause foaming. On the other hand, a re-peelable pressure-sensitive adhesive with improved wettability (occurrence of foaming) due to fluidity tends to increase the adhesiveness at the same time, and particularly the adhesiveness in high-speed peeling (30 m / min, etc.) which is a practical aspect is increased. There was a problem that the workability of the peeling process deteriorated.

  Also known is the technology of a releasable adhesive that uses a small amount of (meth) acrylic acid alkylene oxide adduct as a copolymerizable monomer constituting the base polymer of an acrylic adhesive and further contains a crosslinking agent. (Patent Document 2). However, in this pressure-sensitive adhesive composition, since an acrylamide monomer is added, the glass transition temperature becomes high and the wettability is lowered, so that both wettability and high-speed peelability are insufficient.

  In addition, in order to solve these problems, as a re-peelable pressure-sensitive adhesive that can be easily peeled at high speed and has excellent wettability, the amount of (meth) acrylic acid alkylene oxide adduct is increased and a crosslinking agent is contained. Removable adhesives that have been removed are also known. (Patent Document 3) However, in this pressure-sensitive adhesive composition, although the wettability and the adhesive strength at high speed peeling are improved, the adhesive strength at high speed peeling is about 20 times the adhesive strength at low speed peeling. Therefore, it is not suitable for applications requiring high adhesion and high-speed peelability. Moreover, since the (meth) acrylic-acid alkylene oxide adduct is expensive compared with the (meth) acrylic-acid alkylester, manufacturing cost becomes high.

JP-A-8-85779

JP-A-5-9449

Japanese Patent Laid-Open No. 2005-200540

  The present invention proposes a pressure-sensitive adhesive composition for a surface protective sheet, which has high adhesive strength but has low adhesive strength at high-speed peeling and good wettability.

  As a result of intensive studies, the inventors of the present invention set the theoretical glass transition temperature of the acrylic polymer copolymerized with the (meth) acrylic acid alkylene oxide adduct to a certain range, and specified the (meth) acrylic acid alkylene oxide adduct to a specific range. In order to complete the present invention, it is found that by performing polymerization by a polymerization method, a pressure-sensitive adhesive composition having high adhesive strength, excellent high-speed peelability, good wettability, and low cost can be obtained. It came.

That is, the pressure-sensitive adhesive composition for a surface protective sheet of the present invention is
In the polymerization, a component (hereinafter referred to as “component (A)”) containing 3 to 40% by weight of a (meth) acrylic acid alkylene oxide adduct based on the total amount of the polymerizable monomer, and the (meth) acrylic acid alkylene oxide addition A component containing 60 to 97% by weight of a polymerizable monomer other than the above-mentioned polymerizable monomer (hereinafter referred to as “component (B)”) is separately and simultaneously started dropwise, and the component (A) A (meth) acrylic polymer having a theoretical glass transition temperature of −50 ° C. to 0 ° C. obtained by drop polymerization in which the time until the end of dropping is 1/4 to 2/4 of the time until the end of dropping of the component (B). The most important feature is that it is obtained by blending with a crosslinking agent.

  Moreover, this invention provides the surface protection sheet formed by coating the said adhesive composition on a support body.

  (Meth) acrylic acid alkylene oxide adduct is copolymerized by a limited method, and (meth) acrylic polymer with a limited theoretical glass transition temperature has a high adhesive force, but at a high speed peeling than a low speed peeling. Therefore, it is possible to provide a surface protective sheet that can be peeled off with a low force and has good wettability at low cost.

(Polymerizable monomer)
The pressure-sensitive adhesive composition for a surface protective sheet of the present invention uses a component (A) and a component (B) containing the following polymerizable monomer, and is obtained (meth) acrylic polymer (acrylic (co) polymer). Is crosslinked with a crosslinking agent.
Component (A): Component containing 3 to 40% by weight of (meth) acrylic acid alkylene oxide adduct based on the total amount of polymerizable monomer Component (B): A polymerizable monomer other than component (A) is a polymerizable monomer Ingredients 60 to 97% by weight based on the total amount

  The polymerizable monomer contained in the component (B) preferably contains a (meth) acrylic monomer other than the (meth) acrylic acid alkylene oxide adduct, and more preferably a (meth) acrylic acid alkylene oxide adduct. More preferably, it consists of one or more (meth) acrylic monomers other than the above.

  Examples of the (meth) acrylic acid alkylene oxide adduct contained in the component (A) include alkoxy polyethylene glycol (n = 1 to 30) (meth) acrylate, alkoxy polypropylene glycol (n = 1 to 30) (meth) acrylate, and the like. Can be mentioned. Of these, methoxypolyethylene glycol (meth) acrylate is preferable from the viewpoint of flexibility, and n = 5-20 is particularly preferable. In addition, n shows the average added mole number of ethylene oxide.

  It is preferable that the (meth) acrylic-acid alkylene oxide adduct contained in a component (A) is 1-50 mass% with respect to the polymerizable monomer whole quantity, More preferably, it is 3-40 mass%. When the (meth) acrylic acid alkylene oxide adduct is less than 3% by mass, the wettability of the pressure-sensitive adhesive is lowered. On the other hand, when it exceeds 40% by mass, the adhesive force during high-speed peeling increases.

  As the (meth) acrylic monomer that can be preferably used as the polymerizable monomer contained in the component (B), a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms can be used. Examples include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. it can. These are used alone or in combination. Among these (meth) acrylic acid alkyl esters, it is preferable to carry out copolymerization using (meth) acrylic acid alkyl esters having an alkyl group having 2 to 12 carbon atoms in terms of tackiness.

  Functional group-containing (meth) acrylic monomers that can be preferably used as the polymerizable monomer contained in component (B) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, ( Examples thereof include hydroxyl group-containing monomers such as 4-hydroxybutyl methacrylate and monoglyceryl (meth) acrylate; and carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, and itaconic acid. These are used alone or in combination.

  It is preferable that a functional group containing monomer is 0.1-10 mass% with respect to the polymerizable monomer whole quantity, More preferably, it is 0.5-6 mass%. If the functional group-containing monomer is less than 0.1% by mass, the degree of crosslinking and cohesion as an adhesive is insufficient, while if it exceeds 10% by mass, the degree of crosslinking becomes too high, resulting in zipping during high-speed peeling and wettability. Therefore, it becomes impossible to re-apply the surface protection sheet, and the production efficiency also deteriorates.

[(Meth) acrylic polymer]
The polymerizable polymer contained in the component (A) and the polymerizable polymer contained in the component (B) are polymerized to obtain a (meth) acrylic polymer. In the present invention, when the (meth) acrylic polymer is polymerized, the component (A) and the component (B) are separately and simultaneously started to be dropped and polymerized, and the time until the dropping of the component (A) is determined as the component (B ) Is required to be 1/4 to 2/4 of the time until the completion of dropping. When the component (A) is faster than 1/4 of the time until the end of dropping of the component (B) or slower than 2/4, the wettability is deteriorated.

  The reason for this is not necessarily clear, but the copolymerizability of the (meth) acrylic acid alkylene oxide adduct is more than that of other polymerizable monomers, particularly (meth) acrylic monomers that are not (meth) acrylic acid alkylene oxide adducts. Since it is slow, it is considered that it was possible to uniformly copolymerize by adding it to the polymerization system to some extent at the initial stage of polymerization, and this is considered to have achieved both wettability and high-speed peeling force.

  The above polymerization method is intended to finish dropping the component (A) before the component (B), and if this intention is satisfied, the components (A) and a part of the component (B) are transferred first. The solution may be dropped and polymerized, and then the component (B) may be dropped.

  In general, when a polymer is obtained from a polymerizable monomer, a polymerization initiator is added to the monomer component. In the present invention, when a (meth) acrylic polymer is prepared by dropping polymerization, a polymerization initiator is added to the component (A) and / or the component (B) in addition to the polymerizable monomer. Drop polymerization can be performed. In this invention, since a component (A) complete | finishes dripping earlier than completion | finish of dripping of a component (B), it is preferable to add a polymerization initiator at least to a component (B).

  A well-known thing can be used as a polymerization initiator without a restriction | limiting. Specific examples of the compound include azo compounds such as azobisisobutyronitrile (AIBN) and peroxides such as benzoyl peroxide and cumene peroxide, but are not limited thereto.

  The (meth) acrylic polymer may have a weight average molecular weight in the range of 100,000 to 1,500,000. Furthermore, it is preferable that it is the range of 200,000-1 million. When the weight average molecular weight is 100,000 or less, the wettability is improved and the adhesive force at high-speed peeling is increased, and when it is 1.5 million or more, the wettability is insufficient.

  In the present invention, the glass transition temperature of the (meth) acrylic polymer is required to be −50 ° C. to 0 ° C. When the glass transition point of the polymer is higher than 0 ° C., the wettability cannot be maintained, and when the glass transition point is lower than −50 ° C., the adhesive force at high speed peeling is increased. If it is higher or lower than the above range, the balance between the wettability and the adhesive force at high speed peeling cannot be maintained.

  Further, in the (meth) acrylic polymer of the present invention, the crosslinking agent reacts with these functional groups to form a crosslinked structure by copolymerizing the functional group-containing monomer, so that the balance between adhesive force and removability is balanced. A good pressure-sensitive adhesive can be obtained.

[Surface protective sheet pressure-sensitive adhesive composition]
The pressure-sensitive adhesive composition for a surface protective sheet of the present invention can be obtained by crosslinking reaction of the (meth) acrylic polymer with a crosslinking agent. As the crosslinking agent, a compound having an isocyanate group such as a known trifunctional isocyanate or diisocyanate compound, a compound having a bisidyl group or a trifunctional or higher glycidyl group (epoxy compound), or a metal chelate compound can be suitably used. . These compounds may be used alone or in combination of two or more.

  Specific examples of the compound having an isocyanate group include, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4 -Aromatic isocyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; adducts of tolylene diisocyanate (3 mol) and trimethylolpropane (1 mol), hexamethylene diisocyanate (3 mol) Trimethylolpropane (1 mol) adduct, isophorone diisocyanate (3 mol) and trimethylolpropane (1 mol) adduct, xylene diisocyanate (3 moles) with an isocyanate adduct of adduct of trimethylol propane (1 mole); and the like.

  Examples of the compound having a difunctional or trifunctional or higher glycidyl group include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6 -Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylamine, diamine glycidylamine, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N' -A compound having two or more epoxy groups in a molecule such as diamineglycidylaminomethyl) cyclohexane.

  Examples of the metal chelate compound include polyvalent metal chelate compounds such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

  In the pressure-sensitive adhesive composition for a surface protective sheet of the present invention, for example, other acrylic pressure-sensitive adhesives can be used in combination as long as the object of the present invention is not impaired. Moreover, you may mix | blend additives, such as a tackifier, antioxidant, a ultraviolet absorber, an antifungal agent, an antifoamer, a pigment, and a vehicle, as needed.

[Surface protection sheet]
The surface protection sheet in which the adhesive layer was formed is obtained by applying the adhesive composition for surface protection sheets of this invention to the surface of a support body, and drying. Examples of the support include various plastic films such as a polyvinyl chloride film, a polyethylene film, a polypropylene film, a polyethylene terephthalate film, a polyurethane film, and a polyamide film, or a uniaxial or biaxially stretched film of these films.

  The surface protective sheet of the present invention can be suitably used as a surface protective sheet for optical members such as liquid crystal displays and plasma displays.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Production of (meth) acrylic polymer]
(Production Example 1)
A four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, cooler, and dropping funnel was charged with 75 parts by weight of ethyl acetate, and 10 parts by weight of M-90G as component (A) was brought to 80 ° C. in a nitrogen gas stream. The mixed solution obtained by adding 46 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 part by weight of polymerization initiator AIBN as a component (B) was added in a nitrogen gas stream at 80 hours. The polymerization was carried out by dropwise addition at 2 ° C. over 2 hours. After completion of the dropping, polymerization was carried out at 80 ° C. for 6 hours. After completion of the reaction, it was diluted with toluene to prepare a solid content of 45%, and a (meth) acrylic polymer having a theoretical glass transition temperature of -17 ° C was obtained.

(Production Example 2)
Production Example 1 except that component (A) is M-90G 3 parts by weight, and component (B) is 2EHA 53 parts by weight, MMA 40 parts by weight, 2HEMA 2 parts by weight, AA 2 parts by weight and polymerization initiator AIBN 0.3 parts by weight. Similarly, a (meth) acrylic polymer having a solid glass content of 45% and a theoretical glass transition temperature of -17 ° C was obtained.

(Production Example 3)
Same as Production Example 1 except that component (A) is 35 parts by weight of M-90G, component (B) is 21 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solids content of 45% and a theoretical glass transition temperature of -17 ° C was obtained.

(Production Example 4)
Same as Production Example 1 except that component (A) is 20 parts by weight of M-90G, component (B) is 52 parts by weight of 2EHA, 24 parts by weight of VAc, 2 parts by weight of 2HEMA, 2 parts by weight of AA, and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solid glass content of 45% and a theoretical glass transition temperature of -48 ° C. was obtained.

(Production Example 5)
Same as Production Example 1 except that component (A) is 10 parts by weight of M-90G, component (B) is 40 parts by weight of 2EHA, 46 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solid glass content of −6 ° C. was prepared to a solid content of 45%.

(Comparative Production Example 1)
A four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, condenser, and dropping funnel was charged with 75 parts by weight of ethyl acetate, and as component (B), 56 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, AA2 The mixed solution obtained by adding parts by weight and 0.3 parts by weight of polymerization initiator AIBN was subjected to drop polymerization in a nitrogen gas stream at 80 ° C. for 2 hours. After completion of the dropping, polymerization was carried out at 80 ° C. for 6 hours. After completion of the reaction, it was diluted with toluene to prepare a solid content of 45%, and a (meth) acrylic polymer having a theoretical glass transition temperature of -17 ° C was obtained.

(Comparative Production Example 2)
Same as Production Example 1 except that component (A) is 2 parts by weight of M-90G, component (B) is 54 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solids content of 45% and a theoretical glass transition temperature of -17 ° C was obtained.

(Comparative Production Example 3)
The same as in Production Example 1 except that component (A) is 45 parts by weight of M-90G, component (B) is 11 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA, and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solids content of 45% and a theoretical glass transition temperature of -17 ° C was obtained.

(Comparative Production Example 4)
Same as Production Example 1 except that component (A) is 30 parts by weight of M-90G, component (B) is 56 parts by weight of 2EHA, 10 parts by weight of VAc, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solid glass content of 45% and a theoretical glass transition temperature of -52 ° C. was obtained.

(Comparative Production Example 5)
Same as Production Example 1 except that component (A) is 10 parts by weight of M-90G, component (B) is 16 parts by weight of 2EHA, 70 parts by weight of VAc, 2 parts by weight of HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN. Thus, a (meth) acrylic polymer having a solid glass content of 45% and a theoretical glass transition temperature of 3 ° C. was obtained.

(Comparative Production Example 6)
A four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, cooler, and dropping funnel was charged with 75 parts by weight of ethyl acetate, 10 parts by weight of M-90G as component (A), and 2EHA46 as component (B). A mixed solution obtained by mixing parts by weight, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA and 0.3 parts by weight of polymerization initiator AIBN was subjected to dropwise polymerization at 80 ° C. for 2 hours in a nitrogen gas stream. After completion of the dropping, polymerization was carried out at 80 ° C. for 6 hours. After completion of the reaction, it was diluted with toluene to prepare a solid content of 45%, and a (meth) acrylic polymer having a theoretical glass transition temperature of -17 ° C was obtained.

(Comparative Production Example 7)
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, a cooler, and a dropping funnel, 75 parts by weight of ethyl acetate, 10 parts by weight of M-90G as component (A), and component (B) A mixed solution obtained by mixing 46 parts by weight of 2EHA, 40 parts by weight of MMA, 2 parts by weight of 2HEMA, 2 parts by weight of AA, and 0.3 parts by weight of polymerization initiator AIBN was charged without dropping, and 8% at 80 ° C. in a nitrogen gas stream. Time polymerization was performed. After completion of the reaction, it was diluted with toluene to prepare a solid content of 45%, and a (meth) acrylic polymer having a theoretical glass transition temperature of −17 ° C. was obtained.

Table 1 shows the theoretical glass transition temperature (Tg) of the (meth) acrylic polymer obtained in the above production example, and Table 2 shows the theoretical glass transition temperature (Tg) of the (meth) acrylic polymer obtained in the comparative production example. Indicated. The theoretical glass transition temperature of the (meth) acrylic polymer obtained in the above production example is obtained from the following FOX formula (1) as the glass transition temperature (Tgn, ° C.) of the homopolymer by each monomer.
1 / (Tg + 273) = Σ [Wn / (Tgn + 273)] (1)
Tg is the glass transition temperature (° C.) of the (meth) acrylic polymer, Wn is the mass fraction of each monomer, Tgn is the glass transition temperature (° C.) of the homopolymer of each monomer, and n is the type of each monomer.

In addition, the glass transition temperature Tgn of each homopolymer is as follows.
2EHA: -70 ° C, 2HEMA: 55 ° C, VAc: 32 ° C, MMA: 105 ° C, AA: 106 ° C, M-90G: -69 ° C

In the text, the meanings of the symbols in the table are as follows.
(Acrylic monomer)
2EHA: 2-ethylhexyl acrylate AA: acrylic acid 2HEMA: 2-hydroxyethyl methacrylate MMA: methyl methacrylate VAc: vinyl acetate M-90G: methoxypolyethylene glycol methacrylate (EO 9 mol adduct) manufactured by Shin-Nakamura Chemical Co., Ltd. (Note: EO: ethylene oxide)
(Polymerization initiator)
AIBN: Azobisisobutyronitrile

[Production of pressure-sensitive adhesive composition and surface protective sheet]
Example 1
"Coronate L" (registered trademark, manufactured by Nippon Polyurethane Industry Co., Ltd.), which is an adduct of tolylene diisocyanate (3 mol) and trimethylolpropane (1 mol) as an isocyanate-based crosslinking agent, 100 parts by weight of the polymer obtained in Production Example 1. ) Using 2.5 parts by weight, a crosslinkable composition solution was obtained. The obtained solution was applied onto a 55 μm thick polyethylene (hereinafter abbreviated as “PE”) film (corona-treated surface) so that the thickness after drying was 6 μm, and the solvent was removed at 70 ° C. A pressure-sensitive adhesive composition for a surface protective sheet was obtained. A 55 μm-thick PE film (non-corona-treated surface) was bonded to the dried surface of this pressure-sensitive adhesive composition, and aged for 7 days in an atmosphere of 23 ° C. and 65% humidity to prepare a surface protective sheet.

(Example 2)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Production Example 2 was used.

(Example 3)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Production Example 3 was used.

Example 4
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Production Example 4 was used.

(Example 5)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Production Example 5 was used.

(Comparative Example 1)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 1 was used.

(Comparative Example 2)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 2 was used.

(Comparative Example 3)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 3 was used.

(Comparative Example 4)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 4 was used.

(Comparative Example 5)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 5 was used.

(Comparative Example 6)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 6 was used.

(Comparative Example 7)
A surface protective sheet was produced in the same manner as in Example 1 except that 100 parts by weight of the polymer obtained in Comparative Production Example 7 was used.

〔Evaluation methods〕
The surface protection sheets of the above examples and comparative examples were tested for low speed peel strength, high speed peel strength, and wettability by the following methods. Table 3 shows the test results.

(Low speed peeling force)
Each of the above surface protective sheets was cut to 25 mm × 50 mm, the cover PE film was peeled off, and then attached to a SUS304BA steel plate (hereinafter referred to as “BA plate”) and left for 1 hour in an atmosphere of 23 ° C. and humidity 65%. . Thereafter, the pulling speed was 300 mm / min and the force for pulling in the 180 ° direction and starting peeling was defined as the low-speed peeling force.

(High speed peeling force)
Each of the above surface protective sheets was cut to 25 mm × 50 mm, the cover PE film was peeled off, and then attached to a BA plate, and left for 1 hour in an atmosphere of 23 ° C. and humidity 65%. Thereafter, the force at which the film was pulled in the 180 ° direction at a peeling speed of 30 m / min and started to peel was defined as a high-speed peeling force.

(Wettability)
Each said surface protection sheet was cut | judged to 25 mm x 50 mm, the PE film for covers was peeled, and then the wetting speed when it was affixed on the BA board was visually observed. Evaluation was made according to the following criteria.
○: Wet.
X: Almost not wet.

  As shown in Table 3, the surface protective sheet using the pressure-sensitive adhesive composition of the example had a high speed peeling force lower than the low speed peeling force. Furthermore, the wettability with respect to the BA plate was also excellent.

The pressure-sensitive adhesive composition for a surface protective sheet of the present invention can provide a surface protective sheet having a high speed peel force lower than a low speed peel force and good wettability. Accordingly, the surface protective sheet using the pressure-sensitive adhesive composition for the surface protective sheet of the present invention is not easily peeled off after being attached, but is easily peeled off at a high speed and can be advantageously used for various surface protections. The utility value above is high.

Claims (5)

  Obtained by blending a (meth) acrylic polymer obtained by polymerizing a polymerizable monomer containing 3 to 40% by weight of the (meth) acrylic acid alkylene oxide adduct with respect to the total amount of the polymerizable monomer, and then crosslinking it with a crosslinking agent. A pressure-sensitive adhesive composition for a surface protective sheet.   The pressure-sensitive adhesive composition for a surface protective sheet according to claim 1, wherein the theoretical glass transition temperature of the (meth) acrylic polymer is -50 ° C to 0 ° C.   The pressure-sensitive adhesive composition for a surface protective sheet according to claim 1 or 2, further comprising a (meth) acrylic monomer other than the (meth) acrylic acid alkylene oxide adduct as the polymerizable monomer. In the polymerization, the (meth) acrylic polymer includes a component containing the (meth) acrylic acid alkylene oxide adduct and a component containing other polymerizable monomer other than the (meth) acrylic acid alkylene oxide adduct. Start dripping separately at the same time,
It is obtained by dropping polymerization in which the time until the dropping of the (meth) acrylic acid alkylene oxide adduct is finished is ¼ to 2/4 of the time until the dropping of the other polymerization monomer is finished. The pressure-sensitive adhesive composition for a surface protective sheet according to any one of claims 1 to 3. The surface protection sheet formed by coating the adhesive composition for surface protection sheets in any one of Claims 1-4 on a support body.