JPS598298B2 - Polyolefin-based removable protective film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyolefin-based peelable protective film.

Peelable protective film is suitable for metal products, plastic products,
Scratches during processing, transportation or storage of rubber products, etc.
It is a material that is temporarily coated on a surface to prevent contamination and corrosion, and can be easily and integrally peeled off after the above purpose has been achieved.

Therefore, the following performance is required of the removable protective film. (a) Appropriate adhesion to the base material.

(The peel strength must be in the range of 100 to 5009/inch.) (b) It must be possible to peel off integrally and continuously during peeling.

(c) There is little change in adhesion over time.

(d) No tackiness.

(e) Do not contain plasticizers, solvents, etc. that may contaminate the surface of the base material.

(f) Items used in processing metal products must be suitable for cold working.

(g) It should be easy to dispose of after use.

Until now, it has been used as a removable protective material especially during drawing and roll processing of metal materials such as aluminum plates and stainless steel plates. As necessary, polyvinyl chloride organosols, plastisols, or polyvinyl chloride films coated with an adhesive on one side have been used. However, since the polyvinyl chloride-based protective material contains a plasticizer and an organic solvent, it is undesirable from the viewpoint of the working environment during baking or the generation of air pollution. Furthermore, polyvinyl chloride-based removable protective films have the problem that when disposing of the film after peeling, a normal incinerator cannot be used because it generates hydrogen chloride when incinerated, so an alternative to polyolefin is desired. There is. However, in order to use polyolefin film as a removable protective film, the following problems must be solved.

The first point is that polyolefins do not have adhesive properties to metals. To address this issue, methods have been developed to date, including methods for incorporating adhesion-imparting substances into polyolefins;
Also, a method of providing an adhesive layer between polyolefin and metal has been proposed. Among these methods, as a method of incorporating an adhesion-imparting substance into polyolefin, a method has been proposed, for example, a method of blending a tackifying agent such as a hydrocarbon resin or rosin with polyolefin (for example,
No. 8783, Special Publication No. 26339, Special Publication No. 1978-
44928, etc.) However, such a method cannot be used for a removable protective film because the composition has adhesive properties. On the other hand, it is also known that adhesion can be imparted by incorporating a carboxyl group-containing polyolefin. However, for example, Special Publication No. 44-12580, Special Publication No. 4
The methods proposed in Japanese Patent Publication No. 5-27235, Japanese Patent Publication No. 494822, etc. all aim to obtain polyolefin compositions that firmly adhere to metal materials, and as in the present invention, methods that can be easily peeled off by hand. No consideration has been given to protective films so far. Of course, it is not unexpected that a composition having adhesion strength suitable for a removable protective film could be obtained by adjusting the amount of the carboxyl group-containing polyolefin based on the above-mentioned known techniques, but the present invention As a result of their investigation, they found that there is actually no proportional relationship between the amount of carboxyl group-containing polyolefin in polyolefin and the adhesive strength of polyolefin to metal materials, and that adhesion varies greatly depending on the thermal history during coating. Therefore, it has been extremely difficult to adjust the blending amount so as to provide appropriate adhesion.
Moreover, even if the adhesion of such a composition could be adjusted to a range of 100 to 4009/Inch by strictly controlling the coating treatment conditions, the adhesion would gradually increase during storage or transportation. It was observed that peeling became difficult. As described above, polyolefin-based releasable protective films that have adequate adhesion over a long period of time were hardly known prior to this proposal. Another important characteristic of a removable protective film is its suitability for cold working.

Protective films used during metal processing are required not to cut or peel during cold working, and not to adhere to processing jigs. Therefore, for example, an ethylene monovinyl acetate copolymer film is not suitable as a protective film because it is highly adhesive and tends to block during storage.
Furthermore, commonly used polyolefins such as high-density polyethylene, high-pressure low-density polyethylene, and polypropylene films peel or break during cold processing, so they cannot be used as they are as protective films. The first object of the present invention is to have adhesion to metal materials to the extent that they can be easily peeled off by hand, and that do not adhere to processing jigs, cut, or peel off when the base material is cold worked. The purpose of the present invention is to provide a polyolefin-based protective film.

Another object of the present invention is to provide a polyolefin-based releasable protective film that can be thermally bonded over a wide temperature range and exhibits little change in adhesion over time after coating. That is, the present invention comprises (a) 99 to 60 parts by weight of a polyolefin having a crystallinity of 40% or less by X-ray diffraction and a hardness of 70 or more by JIS K63Ol hardness test;
) [η] is 0.04 to 0.4, acid value is 5 to 70
This is a removable protective film characterized by being made of a polyolefin composition comprising 1 to 40 parts by weight of a carboxyl group-modified hydrocarbon wax.

The present invention will be explained in detail.

First, in the present invention, the main component is a polyolefin (a) component having a crystallinity of 40 or less by X-ray diffraction and a surface hardness of 70 or more by JIS K63Ol.

The polyolefin referred to in the present invention includes, for example, ethylene, propylene, 1-butene, 1-benzene, 3-methyl-1
-butene, 1-hexene, 3-methyl-1-benzene,
It is a homopolymer or copolymer of 4-methyl-1-benzene or the like. The reason for limiting the amount of polyolefin as component (a) in the removable protective film of the present invention as described above is that the inventors of the present invention investigated the relationship between cold workability and resin properties and found the following fact. Based on that.

(1) The lower the yield point stress of a polyolefin in a tensile test, the less peeling occurs during cold working. Especially crystallinity 40
% or less shows almost no yield point in the stress-elongation curve in one tensile test, and has excellent cold workability. (2) The adhesiveness and surface hardness of polyolefin are correlated.

Then, the surface hardness (hereinafter H
(abbreviated as "s") less than 70 is too sticky and cannot be used. The polyolefin as component (a) in the present invention may be composed of a single polymer or a mixture of two or more polymers.

In either case, the polyolefin component (a) must have a crystallinity of 40% or less, preferably 30% or less, and a surface hardness of 70 or more, preferably 80 or more. Examples of polyolefins that can meet these requirements include those with an ethylene content of 70 to 95 mol% and a density of 0.
．． Examples include polyolefins whose main component is an ethylene-α-olefin copolymer of 80 to 0.90 g/d. Among the ethylene-α-olefin copolymers in the above range, particularly, the ethylene content is 86 to 95 mol%, the density is 0.87 to 0.90 g/d1, the melting point is 60°C to 9
The ethylene-1-butene random copolymer at 0°C has a crystallinity of 5 to 30% and an Hs of 80 or more, and can be used alone or mixed with a carboxyl group-containing hydrocarbon wax described below to form a removable protective film. Can be used.

However, so-called amorphous ethylene-α-olefin copolymers with an ethylene content of 70 to 85 mol% and a crystallinity of less than 5% have an Hs of less than 70 and are sticky, so they cannot be mixed with other polyolefins. Needs to be reformed.

Examples of the polyolefin used in the above modification include high density polyethylene, low density polyethylene, polypropylene, poly-1-butene, propylene-ethylene copolymer with an ethylene content of 10 mol% or less, and an ethylene content of 9
Examples include ethylene-α-olefin random copolymers and ethylene-α-olefin imploc copolymers containing 5 mol% or more. The mixing ratio of these polymers and the amorphous ethylene-α-olefin copolymer is such that the resulting polyolefin composition has a crystallinity of 40% or less and an Hs of 70%.
Any combination may be used as long as it meets the above requirements. According to the present inventors, in the above mixture, amorphous ethylene-α
- It is preferred that the olefin copolymer be in the range of 30 to 80% by weight. For example, in the case of a composition in which component (a) is a two-component composition of low-density polyethylene/ethylene-propylene rubber (ethylene content 78 mol%), the low-density polyethylene is 40 to 70% by weight and the ethylene-propylene rubber is 60% by weight. The range is preferably from 30 parts by weight,
In the case of high-density polyethylene/ethylene-propylene rubber compositions, 30 to 50% by weight of high-density polyethylene
, ethylene-propylene rubber in a range of 70 to 50% by weight is preferably used.

Also low density polyethylene/polypropylene/ethylene-
In a composition consisting of three components of propylene rubber, 20 to 65% by weight of low density polyethylene, 5 to 20% by weight of polypropylene, and 30% by weight of ethylene-propylene rubber.
20 to 65% by weight of low density polyethylene 5/high density polyethylene/ethylene-propylene rubber compositions.
, high density polyethylene 5 to 15% by weight, ethylene-
Propylene rubber in the range of 30 to 65% by weight is preferably used. Of course, such a composition ratio varies depending on the composition of the ethylene-α-olefin copolymer itself, which is the main component. The intrinsic viscosity [η] (measured in decalin at 135° C.) of the polyolefin component (a) is preferably in the range of 1.0 to 3.0 because a film with balanced moldability and strength can be obtained.

Next, in the present invention, a carboxyl group-modified hydrocarbon wax (
(b) component) is used as the second component.

In the present invention, hydrocarbon waxes include, for example, paraffin wax obtained during petroleum refining, microcrystalline wax, wax produced by the Fischer Tropichu method, wax obtained by polymerizing ethylene or propylene, or general polyethylene wax. Refers to wax-like substances made of hydrocarbons, such as wax obtained by thermally decomposing polypropylene. Among these, Fischer-Tropisch wax and polyethylene wax can be preferably used. Especially the density is 0.90 to 0.95
It is most preferable to use a medium-low density polyethylene wax of 9/C7L as a raw material because it has less temperature dependence in adhesion when made into the carboxyl group-modified wax described below. The term "carboxyl group-modified hydrocarbon wax" refers to a wax containing carboxyl groups by oxidative modification of the above hydrocarbon wax or graft modification of the wax with an unsaturated carboxylic acid or its anhydride.

Any known method can be used to oxidize the hydrocarbon wax. Also, known methods can be used to graft the unsaturated carboxylic acid or its anhydride; for example, both are heated to high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator. It is done by certain things. Other vinyl monomers such as styrene may be present during the reaction. Examples of unsaturated carboxylic acids or anhydrides thereof include acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, citraconic anhydride, itaconic acid, and itaconic anhydride.

In a hydrocarbon wax that has been oxidatively modified or graft-modified with an unsaturated carboxylic acid or its anhydride, some of the carboxyl groups may be further esterified, amidated, imidized, or metal chlorinated. In the present invention, the carboxyl group-modified hydrocarbon wax has [η] of 0.04 to 0.4.
, preferably 0.07 to 0.2, acid value 5 to 7
0, preferably in the range of 10 to 50. The second point of focus of the present invention is that by blending such a specific polymer (b) component with the polyolefin (a) component, it has the appropriate adhesion to metal necessary for a removable protective film. In addition, it has been found that a film can be obtained that exhibits less change in adhesion due to thermal history during coating and less change in adhesion over time. Carboxyl group-containing polymers with [η] greater than 0.4 cannot be used because their adhesion is highly temperature dependent, as shown in the comparative example below, and their adhesion is too large to peel.

On the other hand, a modified wax with [η] of less than 0.04 has a low softening point and is not practical because it oozes out and contaminates the substrate. Modified waxes with an acid value of 5 or less have poor adhesion to metal materials, while those with an acid value of more than 70 have poor compatibility with component (a), making it impossible to obtain a uniform film. In the peelable protective lime of the present invention, the ratio of component (a) to component (b) is 99 to 60 parts by weight, preferably 95 to 7 parts by weight.
0 parts by weight to 1 to 40 parts by weight, preferably 5 to 3 parts by weight
It is necessary that the content of component (b), the carboxyl group-modified hydrocarbon wax, is less than the above range, and the adhesion of the film to metal will be poor; on the other hand, if it is too much, the film will become brittle, making it difficult to use in practical use. Can not. In addition to the polyolefin (a) component and the carboxyl group-modified hydrocarbon wax (b) component, the polyolefin composition that is the material for the protective film of the present invention includes a heat stabilizer, a weather stabilizer, and the like, within the range that does not impair the purpose of the present invention. It may contain pigments, dyes, fillers, nucleating agents, anti-blocking agents, lubricants, slip agents, antistatic agents, plasticizers and the like.

In particular, when a weathering stabilizer is added to the above composition in an amount of about 0.1 to 1.0% by weight, it has the effect of preventing changes in adhesion over time when the base material is left outdoors after being coated with a protective film. When used as a protective film, it is preferably blended. A well-known method can be used to obtain a protective film from the above-mentioned materials.

For example, each component is granulated in a separate kneading machine, or simply mixed without granulation, and then plasticized in an extruder, kneader, etc., and then extruded by the well-known inflation method or T-die method. Can be molded. The resin temperature during film molding is preferably 150 to 250°C. The thickness of the protective film is preferably in the range of 40 to 300μ.

The temperature at which the peelable protective film of the present invention is thermally bonded to a metal material may be at least the melting point of the film, and is usually 8.
It is preferable to carry out in the range of 0 to 24'C.

The releasable protective film of the present invention has an appropriate adhesion to metal that can be peeled off by hand.

Furthermore, changes in adhesion due to thermal history during coating and changes over time in adhesion are small. It also has excellent cold processing suitability.
It has most of the properties required for a removable protective film, such as not breaking or peeling during cold pressing of metals, and not having adhesive properties. Furthermore, since the protective film of the present invention has polyolefin as its main component, when it is disposed of after use, it can be easily incinerated without using a special furnace unlike conventionally used polyvinyl chloride protective agents. Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist thereof is exceeded. Example 1 Ethylene-1-butene random copolymer (melt index (190 C), 4.01 ethylene content 91 mol%, density 0.8879/CTit, crystallinity 17%,
Polyethylene wax ([η] = 0.0
9. Density 0.930L4 Acid value 501 Softening point (ring and ball method)
At 115°C, 5 parts by weight of the raw material wax (density 0.908 g/~) were mixed and then granulated using an extruder.

The obtained pellets were molded into a film having a thickness of 100 μm using a conventional T-die film molding machine for thermoplastic resins.
Next, a degreased stainless steel plate of 200 x 200 x 0.2 mm was preheated at 60°C, the above film was preliminarily bonded with a rubber roll, and then heated in a heating oven for 130°C for 5 minutes and 15°C.
The film was bonded by reheating under four conditions: -10 minutes, 1700C - 3 minutes, and 200C - 5 minutes.

The film-coated stainless steel plate obtained by the above method was cut into a strip with a width of 1 inch, and was
Peeling was performed at 1800 mm/min. 170C again
- The stainless steel plate laminated with the film for 3 minutes was left in a high temperature and high humidity tank at 65°C and 80RH for one week,
A peel test was also conducted on the sample that had been left in a weather-o-meter for 100 hours.

Example 2 Polyethylene wax ([η] = 0.15, density 0.9) grafted with 90 parts by weight of the ethylene-1-butene random copolymer used in Example 1 and 1.5% by weight of acrylic acid
289/CTitl acid value 301, softening point 112°C, raw material wax density 0.913 g/~) 10 parts by weight was used, and the same as Example 1 except that the base material was a 0.2 mm thick aluminum plate. I did the same.

Example 3 70 parts by weight of the ethylene-1-butene random copolymer used in Example 1 and oxidized polyethylene wax (
[η] = 0.14, density 0.941g/~, acid value 16,
Softening point: 1080 C1 Raw material wax density: 0.9229/
Example 1 was carried out in the same manner as in Example 1 except that 30 parts by weight of the composition was used.

Example 4 90 parts by weight of the ethylene-1-butene random copolymer used in Example 1 and partially saponified calcium of oxidized polyethylene wax ([η] = 0.12, density 0.9849/
C7ll softening point 1200C1 acid value 15, calcium content 0.5% by weight, raw wax density 0.9459/~)
The same procedure as in Example 1 was conducted except that a composition consisting of 10 parts by weight was used and the base material was a steel plate with a thickness of 0.1 mm.

Example 5 [η]=0.17, density 0.9819/CI? L1 acid value 28, softening point 126℃, raw material wax density 0.960
The same procedure as in Example 3 was carried out except that oxidized wax of 9/CTit was used.

Comparative Example 1 Sodium salt of ethylene-methacrylic acid copolymer (trade name) was used instead of acrylic acid grafted polyethylene wax.
The same procedure as in Example 2 was carried out except that a composition containing Surlyn Al6Ol, manufactured by Mitsui Polychemical Co., Ltd., melt index 1.2) was used.

Comparative Example 2 Maleic anhydride grafted polyethylene ([η
] = 2.0, and the density was 0.9659/(ILl acid value 45).

The results of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 1. Example 6 Ethylene-1-butene random copolymer (
Melt index 201 ethylene content 93 mol%,
Density 0.8949/(-1iL1 crystallinity 23%, melting point 80°C) 55 parts by weight, ethylene-propylene rubber (melt index 4.2, ethylene content 78 mol%, density 0.8249/~, crystallized Example 1 was repeated except that 20 parts by weight of the acrylic acid-grafted polyethylene wax used in Example 2 were used.

Example 7 Low density polyethylene (trade name Mirason M-11, manufactured by Mitsui Polychemicals, melt index 6.5, density 0.
9179/~, crystallinity 57%) 50 parts by weight, ethylene-propylene rubber (melt index 0.8, ethylene content 80 mol%, density 0.8299/CTl, crystallinity 0%) 30 parts by weight, Propylene ethylene copolymer (
A composition containing 5 parts by weight of melt index (230reC) 6.5, ethylene content 4 mol%, crystallinity 58%), and 15 parts by weight of the maleic anhydride grafted polyethylene wax used in Example 1 was prepared. The procedure was carried out in the same manner as in Example 1 except for using.

Comparative Example 3 Instead of the maleic anhydride grafted polyethylene wax, ethylene monovinyl acetate copolymer (trade name Evaflex P-1905, manufactured by Mitsui Polychemicals, melt index 2.5, vinyl acetate content 19% by weight, density 0. 949/d) and the same procedure as in Example 7 except that an aluminum plate was used as the base material.

Comparative Example 4 Acrylic acid grafted propylene-ethylene copolymer ([
η] = 0.501 ethylene content 4 mol%, acid value 34)
The same procedure as in Example 7 was conducted except that a steel plate was used as the base material.

The results of Examples 6 and 7 and Comparative Examples 3 and 4 are shown in Table 2.

Examples 8 to 11 The composition of Example 2 was further blended with the weathering stabilizer shown in Table 3, and films were molded in the same manner as in Example 1.

Next, it was preliminarily bonded to a base material in the same manner as in Example 1, and then reheated at 170° C. for 3 minutes in a heating furnace. The sample obtained by the above method was left in a weather-o-meter for 100 hours, and the adhesive strength before and after the test was determined. The results are shown in Table 3.

Examples 12 to 14 Press sheets with a thickness of 3 mm were molded from the compositions used in Examples 1, 6, and 7, and the surface hardness of the sheets was measured according to the method of JIS K63Ol.

Further, the film-coated stainless steel plates obtained in Examples 1, 6, and 7 were subjected to an Erichsen test by extruding the film-coated stainless steel plates from the coated side using a punch according to the method of JIS Z2247. Comparative example 5~
8 Instead of the ethylene-1-butene random copolymer in Example 1, low-density polyethylene (trade name: Mirason M-11) was used.
, manufactured by Mitsui Polychemical, melt index 6.5, density 0.9179A, crystallinity 57%, comparative example 5), ethylene-propylene copolymer (melt index 1.0
, ethylene content 97.5 mol%, density 0.9359/
Cd, crystallinity 73%, Comparative Example 6), propylene-ethylene copolymer (melt index 6.5, ethylene content 4 mol%, crystallinity 58%, Comparative Example 7), ethylene-propylene rubber ( A test was conducted in the same manner as in Example 12 using a melt index of 0.8, an ethylene content of 80 mol%, a density of 0.8299/Critl crystallinity of 0%, and Comparative Example 8).

The test results of Examples 12 to 14 and Comparative Examples 5 to 8 are summarized in the fourth section.
Shown in the table.

Example 15 50 parts by weight of the ethylene-1-butene random copolymer used in Example 1, melt index (190 body C)4.
0, ethylene content 96 mol%, density 0.9259/~
, 45 parts by weight of ethylene-1-butene copolymer having a crystallinity of 49%, and 5 parts by weight of the maleic anhydride grafted polyethylene wax used in Example 1. The procedure was as in Example 12.

The results are shown below. (1) Adhesiveness Part of it peels off.

Claims (1)

[Scope of Claims] 1 (a) 99 to 60 parts by weight of a polyolefin having a crystallinity of 40% or less according to X-ray diffraction and a hardness of 70 or more according to JIS K6301 hardness test, and (b) [
A removable protective film characterized by being made of a polyolefin composition comprising 1 to 40 parts by weight of a carboxyl group-modified hydrocarbon wax having an acid value of 5 to 70 and a carboxyl group-modified hydrocarbon wax having an acid value of 5 to 70. 2. The film according to claim 1, wherein the polyolefin (a) has a crystallinity of 30% or less as determined by X-ray diffraction. 3. The polyolefin (a) has an ethylene content of 86 to 95 mol% and a density of 0.87 to 0.90 g/cm^
3. The film according to claim 1, which is an ethylene-1-butene random copolymer of No. 3. 4 [η] of the polyolefin in (a) is 1.0 to 3
．． Claim 1 characterized in that it is in the range of 0.
The film described in section. 5. The film according to claim 1, wherein the carboxyl group-modified hydrocarbon wax is a modified product of Fischer-Tropisch wax or polyethylene wax. 6 Polyethylene wax has a density of 0.90 to 0.9
The film according to claim 5, characterized in that it is a polyethylene wax of 5 g/cm^3. 7. The film according to claim 1, wherein the carboxyl group-modified hydrocarbon wax is an oxidation-modified hydrocarbon wax. 8 [η] of carboxyl group-modified hydrocarbon wax is 0
．． The film according to claim 1, characterized in that the film has a particle diameter in the range of 0.07 to 0.2. 9 The weight ratio of component (a) to component (b) is 95 to 70
2. A film according to claim 1, characterized in that the film is in the range of 5 to 30. 10. The film according to claim 1, wherein the polyolefin composition contains 0.1 to 1.0% by weight of a weathering stabilizer.