JPS5814473B2 - Manufacturing method of surface protection sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a surface protection sheet for temporarily protecting the surface of objects such as metal plates, decorative plates, glass plates, wooden plates, etc. In addition, the present invention provides a surface protection sheet that is easily peelable, has good anchoring power with the support, and exhibits excellent workability when working with metal plates.

A surface protection sheet coats the surface of a metal plate to improve workability and prevent scratches on the metal plate surface before the metal plate is subjected to press processing such as punching, bending, drawing, and roll processing. It is necessary to prevent this from happening.

In addition, when using a surface protection sheet for so-called curing, during transportation and storage, dust, iron powder, salts, soot, body fluids and carcasses of insects, droppings of birds and insects, sunlight, wind and rain, etc. It is necessary to prevent scratches, stains, discoloration, contamination, etc. from occurring on the surface due to the impact.

Acrylic acid alkyl esters or polymers containing them as main components have high resistance to light and air, and are excellent in transparency, so they are ideal for the above uses. It is necessary to provide some additional performance.

The characteristics of the adhesive component required for a surface protection sheet are such that it has adhesive strength suitable for each purpose on the protected surface of objects made of various materials, that the adhesive strength does not change over time, and that it can be reused. It is required that it be easily peeled off, that there is no contamination or residue on the surface to be protected after peeling, and that it has good anchoring properties with the self-supporting sheet.

Conventionally, the general manufacturing method for surface protection sheets that uses adhesive as an adhesive component is to coat one side of a base material such as polyethylene, polypropylene, soft polyvinyl chloride, or paper.
A so-called solution coating method is used in which a solution of a rubber adhesive or an acrylic adhesive dissolved in an organic solvent is applied, dried, and then rolled up.

However, when manufacturing surface protection sheets using the solution coating method, organic solvents that are harmful to health are used, which creates a poor working environment, poses a risk of fire, and causes pollution, while also reducing resource savings. It cannot be said that it is advantageous from a viewpoint.

In order to solve these drawbacks, attempts have been made to manufacture a surface protection sheet by coating the surface of a plastic sheet with a thin layer of hot-melt adhesive in a molten state.

However, when a thin sheet is coated by a method using a hot-melt adhesive, mechanical friction causes destruction of the sheet, making it difficult to apply.

In addition, in most cases, the adhesive used in the solution coating method is used as is, and in such cases, it may be difficult to pelletize the adhesive, or it may be difficult to pelletize the adhesive. There are many bad ones.

In order to solve the above-mentioned drawbacks and further satisfy the above-mentioned required properties, the inventors of the present invention conducted extensive research and as a result, applied and dried an aqueous emulsion composition having the following composition as an adhesive component to a self-supporting sheet. The inventors have discovered that an extremely excellent surface protection sheet can be obtained by crosslinking to form a thin crosslinked acrylic rubber layer, leading to the present invention.

That is, the present invention provides (A) an acrylic acid alkyl ester monomer (alkyl group having 1 to 8 carbon atoms) alone, or optionally a methacrylic acid alkyl ester monomer (alkyl group having 1 to 8 carbon atoms), or (B) 1 to 10 parts by weight of a carboxyl group-containing copolymerizable monomer, (C) 0 parts by weight of a copolymerizable divinyl monomer to 100 parts by weight of a base monomer obtained by adding a vinyl monomer copolymerizable with
．． An aqueous emulsion composition obtained by emulsion copolymerization at a ratio of 0.5 to 5 parts by weight and 0.5 to 10 parts by weight of (D) an N-methylol group-containing copolymerizable monomer or its derivative is applied to a self-supporting sheet. The present invention provides a method for producing a surface protection sheet, which is characterized by drying to form a crosslinked acrylic rubber layer.

The above component (5) is a component that imparts desired tackiness, adhesion, cohesiveness, flexibility, etc. to the aqueous emulsion copolymer composition, and the main component acrylic acid alkyl ester monomer is acrylic acid. Butyl and 2-ethylhexyl acrylate are most suitable, but other acrylic acid alkyl esters having an alkyl group of 1 to 8 carbon atoms may be used, or they may be used in combination.

As the methacrylic acid alkyl ester, methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. are most suitable, but other methacrylic acid alkyl esters with an alkyl group having 8 or less carbon atoms may also be used. , it is also possible to use them together.

Further, copolymerizable vinyl monomers include styrene, vinyl acetate, acrylonitrile, methacrylonitrile, and the like.

Component (B) imparts adhesion to surfaces to be protected such as metals and plastics through carboxyl groups, and also improves the stability of the emulsion.

In addition, it is a monomer that acts as a reaction site for crosslinking by performing a dehydration reaction and dealcoholization reaction with the N-methylol group-containing copolymerizable monomer or its derivative, which is the component (D) described below.Acrylic acid, methacrylic acid , maleic anhydride, itaconic acid, etc.

If the carboxyl group-containing monomer is 10 parts by weight or more based on 100 parts by weight of the base monomer of component (g), the adhesiveness is too high and it becomes difficult to peel it off from the protected surface.
It is unsuitable as an adhesive component for surface protection.

If the amount is less than 1 part by weight, the adhesive and crosslinking function cannot be exhibited, so it is necessary to use 1 to 10 parts by weight.

Next, component C) is a type of so-called internal cross-linking agent, and by copolymerizing it, cross-linking occurs between polymers and moderately increases cohesive force, thereby preventing an increase in adhesive strength after pasting. It is a component that makes it possible to process metal sheets and provides excellent workability when processing metal plates.

This monomer includes polyethylene glycol dimethacrylate, polyethylene glycol diacrylate,
Divinylbenzene, other acrylic acid, methacrylic acid,
Examples include allyl esters of maleic acid, fumaric acid, and itaconic acid.

If the amount of component (C) is less than 0.05 parts by weight, no effect will be observed at all, and if it is more than 5 parts by weight, crosslinking may occur excessively, resulting in decreased adhesiveness and poor processability. It is necessary to use 0.5 to 5 parts by weight.

The component fD) performs a dehydration reaction and dealcoholization reaction with the carboxyl group described above, and also acts as a self-crosslinking monomer by performing self-condensation.

Since it is a type of so-called internal crosslinking agent, it is possible to provide desired adhesive properties without adding a new crosslinking agent from the outside.

Therefore, there are drawbacks that have been difficult to solve in the prior art, namely, when a crosslinking agent is added to an emulsion polymer, the stability of the emulsion deteriorates, and it is difficult to uniformly mix the crosslinking agent.

Furthermore, it has the feature of being able to solve problems such as the need for a mixing process all at once.

However, a small amount of external cross-linking agent may be used in combination, paying due attention to the above-mentioned problems.

This monomer includes N-methylol acrylamide,
There are N-methylolmethacrylamide, N-butoxymethylacrylamide, etc. If it is less than 0.5 parts by weight, it has very little effect as a crosslinking agent and the cohesive force of crosslinked acrylic rubber is insufficient, and if it is more than 10 parts by weight, crosslinking becomes excessive. Since the crosslinked rubber becomes too hard and the polymerization stability deteriorates, it is necessary to use 0.5 to 10 parts by weight.

The aqueous emulsion composition obtained using the above components (A) to (D) is produced by a self-condensation reaction between the active groups of the N-methylol group-containing copolymerizable monomer or its derivative in the copolymer constituting the aqueous emulsion, The dehydration and dealcoholization reactions between the group and the active group of the N-methylol group-containing copolymerizable monomer or its derivative in the copolymer are achieved by coating and drying an aqueous emulsion on a self-supporting sheet. It is something that
It is not always necessary to add a crosslinking agent as in the conventional case.

Moreover, the crosslinked acrylic rubber layer obtained by the present invention is
Good anchoring properties for self-supporting sheets, especially polyolefin sheets.

This is done by applying an aqueous emulsion to a polyolefin sheet that has been surface-treated (corona treatment, sputtering treatment, flame treatment, chemical treatment) and drying it, so that the active groups on the surface of the oxidized polyolefin sheet become copolymerized to form the aqueous emulsion. It is presumed that it is obtained by reacting with the active group of the N-methylol group-containing copolymerizable monomer or its derivative in combination.

By the way, as a rice-sensitive adhesive composition using an N-methylol group-containing copolymerizable monomer, Japanese Patent Laid-Open No. 50-11
3539, JP 53-7928, JP 51-308
There are 93.

These are considered to be copolymers based on the components A), B), and D) above, but when applied as a pressure-sensitive adhesive for surface protection sheets, the adhesion after pasting to the protected surface It is difficult to prevent the force from increasing.

In the aqueous emulsion composition used in the present invention, predetermined amounts of a carboxyl group-containing copolymerizable monomer, a copolymerizable divinyl monomer, and an N-methylol group-containing copolymerizable monomer or a derivative thereof are added to the pace monomer as an emulsifier. It is obtained by emulsion polymerization of a monomer aqueous emulsion mixture containing a nonionic surfactant, an anionic surfactant, etc. using a polymerization initiator.

The copolymer aqueous emulsion composition thus obtained can be used as it is, but in order to adjust the coating viscosity, it is thickened with ammonia, amine, etc. to a viscosity of 1 to 5.
It is preferable to use an aqueous emulsion with about 0 voids (20° C.).

The above aqueous emulsion composition is applied to one side of a self-supporting sheet such as polyethylene, polypropylene, flexible polyvinyl chloride, paper, etc. to a dry thickness of Q. The crosslinked acrylic rubber layer is formed by coating the rubber layer to a thickness of 0.05 mm or less and drying at a temperature of about 100 to 170° C. for 2 to 10 minutes, thereby producing the surface protection sheet of the present invention.

Next, Examples and Reference Examples of the present invention will be shown, but the present invention is not limited to these Examples.

Note that parts in the following text mean parts by weight.

Example 1 In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, the following monomer mixture 2-ethylhexyl acrylate 80 (parts) acrylonitrile
20 Acrylic acid 5 Diethylene glycol dimethacrylate (NK ester 2G manufactured by Shin Nakamura Chemical Co., Ltd.) 0.2N-
Butoxymethylacrylamide
2 polyoxyethylene alkylphenol ether (hereinafter referred to as POAE).

) 5 ion exchange water
160 was charged and heated while stirring under a nitrogen stream, and when the reaction system reached about 65°C, 0.3 parts of ammonium persulfate was added as a polymerization initiator to start the polymerization, and the polymerization reaction was continued for about 3 hours. Let's do it.

After the polymerization was completed, the reaction system was heated to about 75° C. and aged for about 1 hour to obtain an aqueous emulsion composition containing the copolymer.

While stirring the emulsion composition, about 3% aqueous ammonia solution was added dropwise to give a viscosity of about 5 poise (20°C), and 0.1 part of Plysurf A212C (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as a release modifier. After the addition, it is applied onto a polyethylene sheet with a thickness of about 60 μm so that the dry thickness will be about 5 μm, and it is heated and dried at 100° C. for 5 minutes to form a cross-linked acrylic rubber layer, which provides the surface protection of the present invention. The results of various tests on this surface protection sheet are shown in Table 1.

Examples 2-5 below describe examples of monomer mixtures representing other aspects of the invention in place of the monomer mixture of Example 1, using each monomer mixture under the same conditions as Example 1. An aqueous emulsion composition and a surface protection sheet were manufactured and the test results are shown in Table 1.

Reference Example 1 Using the following monomer mixture, an aqueous emulsion and a surface protection sheet were produced according to Example 1, and the test results are also listed in Table 1.

In both Reference Examples 2 and 3, an aqueous emulsion and a surface protection sheet were produced according to Example 1.

The test results are also listed in Table 1.

As is clear from Table 1, the surface protection sheets of Examples 1 to 5 have characteristics suitable for use as surface protection sheets for temporary protection, with little change in adhesive strength over time after pasting onto stainless steel plates. This shows that the anchorage properties, workability, and weather resistance are all good.

Examples 1 and 2 show that a good surface protection sheet can be obtained using self-crosslinking monomers such as N-butoxymethylacrylamide and N-methylolacrylamide.

Examples 3 and 4 show monomer formulations that maintain adhesive strength relatively low and constant, and Example 5 illustrates a monomer formulation that maintains adhesive strength relatively high and constant.

In addition, Reference Example 1 is a system in which the self-crosslinking monomer is not copolymerized, and the adhesive strength increases significantly after pasting the BA stainless steel plate, resulting in adhesive residue. Reference Example 2 is a system in which the copolymerizable divinyl monomer is not copolymerized. In the system, the increase in adhesive strength after pasting the BA board was large, and the peeling after processing was severe; in Reference Example 3,
This indicates that there is no problem with normal machining, but anchor failure may occur in some areas when heavy machining is performed.

Although the above shows the test results when polyethylene sheets were used as the self-supporting sheets, essentially the same results as in Table 1 can be obtained even when other plastic sheets are used.

Regarding the anchoring property test, the crosslinked acrylic rubber layer formed by the method of the present invention was very good against heat-adhesive polyolefin sheets such as polyethylene sheets, whereas Reference Examples 1- The non-linked or cross-linked acrylic rubber layer of No. 3 has poor anchoring properties for polyolefin sheets, and if it is peeled off after being processed into a metal plate, there is a risk of leaving adhesive residue on the metal plate or increasing the peeling force. .

As explained above, according to the present invention, the adhesive force of the crosslinked acrylic rubber layer formed on the self-supporting sheet can be adjusted to a desired value, and the adhesive force changes after being applied to the protected surface. It can be seen that a surface protection sheet with well-balanced properties such as small amount of oxidation, good anchoring properties, and excellent workability of metal plates can be obtained.

Claims (1)

[Claims] 1(A) Acrylic acid alkyl ester monomer (alkyl group with 1 to 8 carbon atoms) alone, or optionally methacrylic acid alkyl ester monomer (alkyl group with 1 carbon atoms)
1 to 10 parts by weight of a carboxyl group-containing copolymerizable monomer, (0 copolymerizable divinyl monomer) -0.05 to 5 parts by weight,
(D) An aqueous emulsion composition obtained by emulsion copolymerization of 0.5 to 10 parts by weight of an N-methylol group-containing copolymerizable monomer or its derivative is coated on a self-supporting sheet and dried to form a crosslinked acrylic rubber layer. A method for manufacturing a surface protection sheet, characterized by forming a surface protection sheet.