JPS5814472B2 - 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, and woodblocks, and in particular, the present invention relates to a method for producing a surface protection sheet for temporarily protecting the surfaces of objects such as metal plates, decorative plates, glass plates, and woodblocks, and in particular, a method for producing a surface protection sheet that causes little change in adhesive strength and The object of the present invention is to provide a surface protection sheet that is easily peelable, has good anchoring power with a support, and exhibits excellent processability when processing 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 fire risk, causes pollution, and is not a resource-saving method. 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 is directed to (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 in combination therewith. (B) 1 to 10 parts by weight of a carboxyl group-containing copolymerizable monomer and (C) a copolymerizable divinyl monomer to 100 parts by weight of a base monomer obtained by adding a copolymerizable vinyl monomer.
(D) a urea formaldehyde initial condensate having two or more alkyl etherified methylol groups, a melamine formaldehyde initial condensate; and adding 1 to 20 parts by weight of a mixture thereof,
The present invention provides a method for producing a surface protection sheet, which is characterized by coating this on a self-supporting sheet and drying it to form a crosslinked acrylic rubber layer.

The aforementioned αN component 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 monomers include butyl acrylate, Although 2-ethylhexyl acrylate is most suitable, 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 meccrylate, 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 objects to be protected such as metals and plastics through its carboxyl group, and also improves the stability of the emulsion.

It is a heptamer that acts as a reaction point for crosslinking through dehydration and dealcoholization reactions with the crosslinking agent described later, and includes 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 the N component, the adhesiveness will be too high and it will be difficult to peel it off from the surface to be protected, making it unsuitable as an adhesive component for surface protection. be.

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 crosslinking agent,
By copolymerizing this, crosslinking between polymers occurs, and cohesive force increases appropriately, making it possible to prevent an increase in adhesive strength after application. As a result, it is possible to take a crosslinked form in which the intermolecular distance between the crosslinking points becomes long, and this is considered to be the reason for the excellent workability during processing of 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.

With respect to 100 parts by weight of the base monomer of the human component, (
If component C) is less than 0.05 parts by weight, no effect will be seen 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.

(As mentioned above, seasonal ingredients are (A), (B), (C)
) is added as an external crosslinking agent to the aqueous emulsion obtained with the monomer composition, and is a urea formaldehyde initial condensate, a melamine formaldehyde initial condensate, or a mixture thereof having two or more alkyl etherified methylol groups as a functional group. used.

These perform a dehydration reaction and a dealcoholization reaction with the component iaB), while also self-condensing, thereby imparting desired adhesive properties and contributing to improved processability of the surface protection sheet and easy peelability after processing.

If it is less than 1 part by weight, no effect will be observed, and if it is more than 20 parts by weight, so-called resinization will occur, making it impossible to use it as a surface protection sheet, so it is necessary to use 1 to 20 parts by weight.

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. It is presumed to be obtained by reacting with a functional alkyl etherified methylol group.

The aqueous emulsion composition used in the present invention contains a nonionic surfactant, an anionic surfactant, etc. as an emulsifier in a predetermined amount of a carboxyl group-containing copolymerizable monomer and a copolymerizable divinyl monomer with respect to the base monomer. A urea formaldehyde initial condensate having two or more alkyl etherified methylol groups, a melamine formaldehyde initial condensate, and a mixture thereof are added to an aqueous emulsion obtained by emulsion polymerizing the blended monomer aqueous emulsion mixture using a polymerization initiator. Obtained by adding.

The aqueous emulsion composition thus obtained can be used as it is, but in order to adjust the coating viscosity, it may be thickened with ammonia, amine, etc. to a viscosity of 1 to 50 poise (
It is preferable to form an aqueous emulsion at a temperature of about 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 0. It is applied to a thickness of 0.5 mm or less, and is applied at a temperature of about 100 to 170 °C to a thickness of 2 to 10 mm.
By drying for a few minutes, a crosslinked acrylic rubber layer is formed to produce 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.

In addition, parts in the following text mean parts by weight.

Example 1 The following monomer mixture was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and heated while stirring under a nitrogen stream until the reaction system reached approximately 65°C. Then, 0.3 part of ammonium peroxide was added as a polymerization initiator to initiate polymerization, and the polymerization reaction was carried out for about 3 hours.

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 containing the copolymer.

While stirring the emulsion, about 3% ammonia aqueous solution was added dropwise to make the viscosity about 5 poise (20°C), and then
As an external crosslinking agent, 10 parts of urea/melamine formaldehyde initial condensate Betsukamine N (manufactured by Dainippon Ink Chemical Industries, Ltd.) in terms of solid content was added to 100 parts of the solid content of the aqueous emulsion, and the mixture was thoroughly stirred and then peeled off. Teflysurf A212C (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 0.
1 part was added, applied to a polyethylene sheet with a thickness of about 60μ so that the thickness after drying was about 5μ, and heated at 100℃ for 5μ.
A crosslinked acrylic rubber layer was formed by heating and drying for a minute to obtain a surface protection sheet of the present invention.

The results of various tests on this surface protection sheet are shown in Table 1.

The following Examples 2 to 4 show other embodiments of heptanomer mixtures for obtaining aqueous emulsions, in which aqueous emulsions were prepared from the following heptanomer mixtures under the same conditions as in Example 1, and then Example 1 After adding an external crosslinking agent and a release regulator in the same manner as above, a surface protection sheet was produced.

The test results are shown in Table 1.

Example 5 To 100 parts (solid content) of the aqueous emulsion obtained in Example 1, 10 parts of melamine formaldehyde initial condensate Betsukamine MAS (manufactured by Inu Nippon Ink Chemical Industry Co., Ltd.) was added as an external crosslinking agent, A surface protection sheet was manufactured according to Example 1.

The test results are shown in Table 1.

Reference Example 1 A surface protection sheet was manufactured according to Example 1 using the same emulsion composition as in Example 1 except that no external crosslinking agent was added.

The test results are also listed in Table 1.

Reference Example 2 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.

Butyl acrylate 85 (parts) Acrylic nitrile 15 Acrylic acid
5POAE
5 ion exchange water 16
0 Reference Example 3 To 100 parts of the solid content of the aqueous emulsion obtained in Reference Example 2, 10 parts of Betscamine N (described above) as an external crosslinking agent was added, and a surface protection sheet was 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 50 exhibited characteristics suitable for use as surface protection sheets for temporary protection, with little change in adhesive strength over time after being applied to stainless steel plates. This shows that both processability and weather resistance are good.

Reference Example 1 shows the results of a system in which no external crosslinking agent was added in Example 1, but the workability test showed that anchoring failure may occur partially in strong working.

Reference example 2 is a system in which the copolymerizable divinyl monomer is not copolymerized and no external crosslinking agent is added, and the adhesive strength increases significantly after pasting to the BA stainless steel plate, resulting in adhesive residue. No. 3 is a system in which the copolymerizable divinyl monomer is not copolymerized, and although there is no adhesive residue after pasting the BA stainless steel plate, it shows significantly poor results in the workability test.

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

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 to 8 carbon atoms)
~8 pieces), or a base monomer made by adding a nahinyl monomer copolymerizable therewith, per 100 parts by weight of (
Aqueous emulsion 1 obtained by emulsion polymerization at a ratio of 1 to 10 parts by weight of B) a carboxyl group-containing copolymerizable monomer and 0.05 to 5 parts by weight of a copolymerizable divinyl monomer (C)
00 parts by weight, (D) 1 to 20 parts by weight of a urea formaldehyde initial condensate, a melamine formaldehyde initial condensate, or a mixture thereof having two or more functional groups of alkyl etherified methylol groups is added. A method for producing a surface protection sheet, which comprises coating and drying a supporting sheet to form a crosslinked acrylic rubber layer.