JPS61268782A - Surface-protection sheet - Google Patents

Abstract

PURPOSE:To produce the titled sheet having excellent processability and high peelability and leaving little residue after peeling, by applying a specific acrylic aqueous emulsion pressure-sensitive adhesive composition to a soft polyvinyl chloride sheet, and drying the emulsion. CONSTITUTION:The objective sheet can be produced by coating a surface of a soft polyvinyl chloride sheet with an acrylic aqueous emulsion pressure- sensitive adhesive composition having crosslinked structure in the particle of the polymer emulsion and obtained by the emulsion-polymerization of a monomer mixture of (A) 100pts.wt. of a monomer composed mainly of a 1-8C alkyl ester of (meth)acrylic acid and (B) 0.1-10pts.wt. of a polyfunctional monomer having >=2 ethylenic double bonds in the molecule, and drying the applied emulsion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a surface protection sheet having a flexible polyvinyl chloride support.

[Conventional technology]

Surface protection sheets are used to coat the surface of a metal plate before pressing or rolling to improve workability and prevent scratches on the metal plate surface. used. In addition, so-called surface protection sheets for curing are provided on the surface of objects such as metal plates while the objects are being stored.

It is also used to prevent scratches, stains, discoloration, and contamination during transportation.

Surface protection sheets used for such purposes are:
It usually consists of a support made of synthetic resin and a pressure-sensitive adhesive layer coated and dried on one side of the support, and is bonded to the surface of the object to be protected with the adhesive layer inside.

In order for the above-mentioned functions to be better exhibited by this lamination, the sheet as a whole must have good properties such as tensile strength, elongation, water resistance, oil resistance, flexibility, and heat resistance. In addition, it is desirable that the adhesive layer has excellent adhesive strength and excellent transparency, and in particular, the adhesive layer must have adhesive strength suitable for each purpose on the protected surface of various objects. , and its adhesive strength does not change over time, and it is easily peeled off when peeled off after use.
It is required that there be no contamination or residue on the protected surface after peeling.

Conventionally, as a surface protection sheet that relatively satisfies these required characteristics, a soft polyvinyl chloride sheet is used as a support, and an alkyl (meth)acrylate is used as a pressure-sensitive adhesive to be applied and dried on this sheet. It is known that an acrylic pressure-sensitive adhesive whose base polymer is an acrylic copolymer containing ester as a main component is used.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional surface protection sheet, while the flexible polyvinyl chloride sheet used as the support contains a considerably large amount of plasticizer relative to the polyvinyl chloride, the acrylic pressure-sensitive adhesive layer provided thereon does not contain the plasticizer. Because the plasticizer has the ability to absorb agents, the plasticizer migrates into this adhesive layer over time, and this migration reduces the adhesive strength of the surface protection sheet and causes deterioration of workability. In addition, the adhesive may remain on the protected surface during peeling, resulting in so-called adhesive residue, which can easily contaminate the protected surface (in addition, the transfer of plasticizer may cause deterioration of the adhesive layer under durability tests, resulting in peeling). This could lead to problems such as difficulties.

In addition, in the conventional surface protection sheet described above, when forming an acrylic pressure-sensitive adhesive layer, an adhesive solution is prepared by dissolving an acrylic copolymer in an organic solvent such as toluene, xylene, or ethyl acetate. However, since this method is applied to a support and dried, there is a risk of deterioration of the working environment and flames due to the use of organic solvents that are harmful to health during the manufacturing stage of the surface protection sheet, and there is also a risk of pollution. In addition, since the support to which the adhesive solution is applied is made of a soft polyvinyl chloride sheet, this support is swollen by the solvent and applied. There were problems such as variations in thickness, elongation of the sheet, and easy breakage during coating.

Therefore, it is an object of the present invention to solve the problems such as a decrease in adhesive strength and adhesive residue caused by the migration of plasticizer in the conventional surface protection sheet, as well as to solve the problems caused by the organic solvent. It is said that

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventor used a specific water emulsion type pressure sensitive adhesive composition as an acrylic pressure sensitive adhesive composition to be applied and dried on a flexible polyvinyl chloride sheet. At that time, he realized that both the problems caused by organic solvents and the problems caused by plasticizers could be solved, leading to the completion of this invention.

That is, the present invention provides a surface protection sheet formed by coating and drying a water emulsion type pressure-sensitive adhesive composition on one side of a soft polyvinyl chloride sheet, wherein the pressure-sensitive adhesive composition has a carbon number of an alkyl group. 1 to 8 (meth)acrylic acid alkyl ester as a main component and ethylenic in the molecule at a ratio of 0.1 to 10 parts by weight per 100 parts by weight of this main monomer. An acrylic water emulsion type adhesive in which the interior of polymer emulsion particles has a crosslinked structure, obtained by emulsion polymerization of a monomer mixture consisting of a polyfunctional monomer having two or more double bonds. The present invention relates to a surface protection sheet comprising a composition.

In this way, in this invention, a water emulsion type adhesive composition that does not use any organic solvent is used as the acrylic pressure-sensitive adhesive composition to be applied and dried on a flexible polyvinyl chloride sheet as a support. In addition to being able to eliminate all the problems caused by the organic solvent, the water emulsion type adhesive composition uses a polymer emulsion particle in which the inside of the particle has a crosslinked structure due to the use of the polyfunctional monomer. As a result, the adhesive layer formed from this forms a strong coating film with strong cohesive force, and even if the plasticizer is transferred to this, problems such as a significant decrease in adhesive strength and adhesive residue, as in the case of conventional methods, will not occur. It has been discovered that a surface protection sheet can be obtained which has excellent processability, good releasability, and less contamination upon peeling.

[Structure and operation of the invention]

The flexible polyvinyl chloride sheet in this invention includes:
Its tensile strength, elongation, water resistance, oil resistance.

Polyvinyl chloride 100 with an average degree of polymerization of about 800-1,200 is generally used as a material with excellent flexibility and heat resistance.
The amount of plasticizer such as dioctyl phthalate or dibutyl phthalate is usually 20 to 20% by weight. A composition containing about 40 parts by weight and a small amount of stabilizers such as metal salts such as lead, cadmium, and barium, phosphates, and organic tin, and various additives such as their +Mn additives is mixed into a solution. A sheet formed by a known method such as a coating method or a roll-forming method is used. The thickness of this sheet is usually 20
It is about 100 μm.

The acrylic water emulsion type pressure sensitive adhesive composition used in this invention has an alkyl group having 1 to 1 carbon atoms.
Emulsion polymerization of a monomer mixture consisting of a main monomer mainly composed of 8 (meth)acrylic acid alkyl esters and a polyfunctional monomer having two or more ethylenic double bonds in the molecule. This can be obtained by

The above main monomer is (meth)acrylic acid having an alkyl group of 1 to 8 carbon atoms, which is a component for imparting tackiness, adhesion, cohesiveness, flexibility, etc. to the adhesive composition. The main component is an alkyl ester, and if necessary, a modifying monomer copolymerizable with the main component is added for the purpose of finely adjusting the adhesive properties and the like.

Of the (meth)acrylic acid alkyl esters 1 which are the main components, butyl acrylate and 2-ethylhexyl acrylate are particularly preferred, and those containing methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. are preferably used. .

Of course, other (meth)acrylic acid alkyl esters may be used as long as the alkyl group has 1 to 8 carbon atoms. Modifying monomers include (meth)acrylic acid alkyl esters whose alkyl groups have carbon numbers outside the above range, acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, acrylonitrile, vinyl acetate, and methacrylic acid. Various vinyl monomers such as lonitrile can be used.

The amount of this modifying monomer used is the main component (meta)
The amount should be 50% by weight or less based on the total amount with the acrylic acid alkyl ester. “Also, examples of polyfunctional monomers having two or more ethylenic double bonds in the molecule include polyvalent esters of polyhydric alcohols and (meth)acrylic acid, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,
These include triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethanetetra(meth)acrylate.
Other examples include divinylbenzenes and polyvalent allyl esters.

This polyfunctional monomer is important for creating an appropriate crosslinked structure in the acrylic copolymer obtained by copolymerizing with the main monomer to avoid problems such as a decrease in adhesive strength due to migration of plasticizer. The amount used is 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of the main monomer.
Parts by weight should be removed. If the amount is less than 0.1 part by weight, the above effects cannot be obtained, and if it exceeds 10 parts by weight, the crosslinking density will increase, resulting in a decrease in adhesive strength and adhesive strength, both of which are inappropriate.

In order to carry out emulsion polymerization of a monomer mixture consisting of such a main monomer and a polyfunctional monomer, a nonionic surfactant or anionic surfactant is used with the above monomer mixture as an emulsifier. The mixture is emulsified and dispersed in water, and an appropriate polymerization initiator such as a persulfate is added thereto, and the polymerization is carried out at a temperature of usually 40 to 90°C for 2 to 1 hour.
It is sufficient to react for 0 hours.

The water emulsion type composition obtained by this method has a structure in which the acrylic copolymer constituting the emulsion particles is appropriately crosslinked, and this composition can be used as it is as the water emulsion type pressure sensitive adhesive according to the present invention. It is used either as a composition or by adding ammonia, amine, etc. to thicken it to a coating-enabled viscosity.

The solid concentration of such a water emulsion type pressure-sensitive adhesive composition is generally about 30 to 60% by weight, and the viscosity is about 1 to 50 voids (at 20°C). This composition may contain known additives such as colorants, fillers, anti-aging agents, etc., if necessary.

In the surface protection sheet of the present invention, the water emulsion type pressure-sensitive adhesive composition having the above structure is coated on one side of the soft polyvinyl chloride sheet so that the thickness after drying is 50 μm or less, preferably 5 to 30 μm. Approximately 100-170
It can be obtained by drying for about 2 to 10 minutes at a temperature of .degree.

Since this sheet has the above-mentioned characteristics, it can be effectively applied to various uses for surface protection such as processing of metal plates and curing.

〔Effect of the invention〕

As described above, in this invention, by using the specific water emulsion type pressure sensitive adhesive composition as the acrylic pressure sensitive adhesive composition to be applied and dried on a soft polyvinyl chloride sheet, organic solvent A surface protection sheet that does not have the problems caused by plasticizer migration in the sheet, has excellent surface protection performance such as workability, has good peelability, and has little contamination when peeled. can be provided.

〔Example〕

Hereinafter, the present invention will be explained in more detail by describing examples. In addition, in the following, parts mean parts by weight.

Example 1 Average degree of polymerization 1,1 (to 100 parts of polyvinyl chloride, 40 parts of dioctyl phthalate, Ba-Zn composite stabilizer 3
A blend consisting of 1 part and 2 parts of blue pigment was kneaded and rolled with calender rolls into a 70 μm thick flexible polyvinyl chloride sheet.

Meanwhile, in a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 75 parts of isobutyl acrylate, 18 parts of acrylonitrile, and 18 parts of acrylic acid were added.
5 parts ion exchange water
30 parts of monomer mixture out of 160 parts, S D 30
．． 3 parts and 112 parts of ion-exchanged water were charged and heated while stirring under a nitrogen stream. When the reaction system reached 65°C, 0.2 parts of ammonium persulfate was added as a polymerization initiator to start polymerization. The polymerization reaction was carried out for about 30 minutes. Then, the remaining monomers, SO3, and water were added dropwise as a monomer emulsion over about 3 hours to continue the polymerization reaction.

After the polymerization was completed, the reaction system was heated to about 75°C and aged for about 1 hour to obtain an emulsion composition containing the acrylic copolymer, and about 2% by weight aqueous ammonia solution was added dropwise with continuous stirring to give about 1 hour of aging. A water emulsion type pressure sensitive adhesive composition having a viscosity of 10 voids (20° C.) was prepared.

This water emulsion type pressure sensitive adhesive composition was applied to one side of the above-mentioned flexible polyvinyl chloride sheet to a thickness of 20 mm after drying.
It was coated to a thickness of .mu.m and dried by heating at 120.degree. C. for 5 minutes to obtain a surface protection sheet of the present invention.

Comparative Example 1 The water emulsion type pressure sensitive adhesive composition of Example 1 was prepared in the same manner as in Example 1, except that 2 parts of polyethylene glycol dimethacrylate, which is one of the monomer components, was not used. A water emulsion type pressure sensitive adhesive composition was prepared, and a surface protection sheet was obtained in the same manner as in Example 1 using this composition.

Comparative Example 2 Instead of the water emulsion type pressure sensitive adhesive composition of Example 1, the monomer mixture described in Example 1 except for 2 parts of polyethylene glycol dimethacrylate was used, using toluene as a solvent. Solution polymerization was carried out, and after this polymerization, the amount of solvent was adjusted to obtain an adhesive solution with an acrylic copolymer concentration of about 20% by weight, and using this solution, a surface protection sheet was produced in the same manner as in Example 1. did.

Example 2 A surface protection sheet was produced in exactly the same manner as in Example 1, except that the following monomer mixture was used.

2-Ethylhexyl acrylate 73.5 parts Methyl methacrylate 20 parts Acrylic acid
5 parts Example 3 A surface protection sheet was produced in exactly the same manner as in Example 1 except that the following monomer mixture was used.

2-Ethylhexyl acrylate 39 parts Butyl acrylate 40 parts Styrene
15 parts acrylic acid
5 parts Example 4 A surface protection sheet was produced in exactly the same manner as in Example 1 except that the following monomer mixture was used.

Butyl acrylate 72 parts Acrylonitrile 20 parts Acrylic acid
For each surface protection sheet of Examples 1 to 4 and Comparative Examples 1 and 2 of 5 parts or more, adhesion test,
The results of the weatherometer durability test and workability test were as shown in the table below. In addition, each test was measured and evaluated as follows.

<Adhesion test> A surface protection sheet was pasted on a 5US304BA finished stainless steel plate with a thickness of 0.4 mm, and the initial adhesion strength and 1 after aging were measured.
The 80 degree peel adhesive force was measured according to JIS Z-1582.゛Weatherometer durability test〉 After pasting the surface protection sheet on the same stainless steel plate as in the adhesion test, load it into the weatherometer.
After a predetermined period of time, the peelability, adhesive residue, and staining of the stainless steel plate surface were examined.

<Workability test> A surface protection sheet was attached to a BA finished stainless steel plate with a diameter of 100n and a thickness of 0.4tm, and the drawing depth was determined using a drawing punch with a punch diameter of 50 mm, both immediately after bonding and after leaving it for 3 months. The damaged state of the sheet when squeezed to a size of 10 cranes.

The floating state of the sheet after processing, the releasability when the sheet was peeled off after processing, adhesive residue, and staining properties were investigated.

As is clear from the above results, the surface protection sheet of the present invention exhibits little change in adhesive strength over time, good peelability after durability tests, less adhesive residue and staining, and excellent workability. It can be seen that it is something that

Claims (1)

[Claims] (1) In a surface protection sheet formed by coating and drying a water emulsion type pressure-sensitive adhesive composition on one side of a soft polyvinyl chloride sheet, the above-mentioned pressure-sensitive adhesive composition has an alkyl group having 1 to 1 carbon atoms. Main monomer mainly composed of 8 (meth)acrylic acid alkyl esters and 100% of this main monomer
obtained by emulsion polymerization of a monomer mixture consisting of a polyfunctional monomer having two or more ethylenic double bonds in the molecule in a ratio of 0.1 to 10 parts by weight to parts by weight, A surface protection sheet comprising an acrylic water emulsion type adhesive composition in which the interior of polymer emulsion particles has a crosslinked structure.