JP2000290622A - Film substrate for tacky adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film for a tacky adhesive tape having characteristics of follow-up properties to curved surfaces and processability at the time of press-processing or the like equal to or higher than those of a vinyl chloride- based film and excellent in weather resistance. SOLUTION: This film substrate for a tacky adhesive tape comprises an acrylic or a methacrylic polymer and has >=0.5 kg/mm2 initial modulus of elasticity, >=1 kg/mm2 breaking strength and >=40% stress relaxation ratio. The glass transition temperature (Tg) of an acrylic or a methacrylic polymer composition constituting the film substrate is, e.g. >=-20 deg.C. A nitrogen-containing monomer such as (meth)acrylamides and a monomer having an acidic group such as a carboxyl group-containing monomer may be contained as constituent monomers in the (meth)acrylic polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film substrate for an adhesive tape having good stress relaxation.

[0002]

2. Description of the Related Art Conventionally, many substrates have been used for the base material of an adhesive tape according to the purpose. Among them, it is important that the base material has excellent stress relaxation properties, in particular, in order to have good adhesiveness without floating at the time of bonding to a curved surface portion or the like at the time of press working or the like. At present, a vinyl chloride-based film is used as a film substrate having such excellent stress relaxation properties and good workability. Recently, polyolefin-based materials have been used in some cases because they are superior to vinyl chloride-based films in terms of stress relaxation, but are excellent in terms of environmental protection.
These adhesive tapes are used in a wide range of fields such as for surface protection and masking.

However, the above-mentioned vinyl chloride-based film and polyolefin-based film have a problem in weather resistance, and when used outdoors for a long period of time, there is a problem that the adhesive tape attached to the film is broken due to deterioration of the film. there were. In addition, when performing strong working such as deep drawing, there are cases where even a vinyl chloride film is insufficient in workability.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a curved surface follow-up property and a workability at the time of press working or the like which are equal to or better than those of a vinyl chloride film, and furthermore, the weather resistance is high. An object of the present invention is to provide an excellent film for an adhesive tape.

[0005]

Means for Solving the Problems In order to achieve the above object, the present inventors have focused on a (meth) acrylic polymer as a material having good weather resistance, and have developed a film made of a (meth) acrylic polymer. As a result of intensive studies on a film with good processability, by designing a polymer so that the initial elastic modulus, rupture strength and stress relaxation rate have appropriate physical properties, it is equivalent to a vinyl chloride film or more. It has been found that a (meth) acrylic film having good processability can be obtained.

That is, the present invention relates to an adhesive comprising a (meth) acrylic polymer, having an initial elastic modulus of 0.5 kg / mm ² or more, a breaking strength of 1 kg / mm ² or more, and a stress relaxation rate of 40% or more. Provide a film base for tape.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The film base material for an adhesive tape of the present invention has an initial elastic modulus of 0.5 kg / mm ² or more, a breaking strength of 1 kg / mm ² or more, and a stress relaxation rate of 40% or more. (Meth) acrylic sheet with

Here, the initial elastic modulus and the breaking strength are values measured using a tensile tester at a film width of 10 mm, a chuck interval of 10 mm, a tensile speed of 50 mm / min, and a measuring temperature of 23 ° C. . The stress relaxation rate was 10 mm under the following conditions: film width: 10 mm, chuck interval: 20 mm, measurement temperature: 23 ° C., and tensile speed: 1000 mm / min.
The stress immediately after stretching at 0% (initial stress) and the stress after standing for 5 minutes while maintaining the stretch amount (5
), And is a value calculated from the following equation. Stress relaxation rate (%) = {((initial stress) − (stress after 5 minutes)) / (initial stress)} × 100

[0009] The initial modulus of elasticity affects the releasability and stress relaxation of the pressure-sensitive adhesive tape. In particular, the stress relaxation is closely related. 0.5 kg as the initial elastic modulus
/ Mm ² or more, preferably 0.5 to 50 kg / mm ² , more preferably 1.0 to 40 kg / mm ² . When the initial elastic modulus is less than 0.5 kg / mm ² , the workability of sticking and peeling is reduced, and the workability of not following a curved surface or floating during press working is also reduced.
Even if the initial elastic modulus is too high, workability may deteriorate.

The breaking strength is 1 kg / mm ² or more, preferably 1 to 10 kg / mm ² , more preferably 1.5 to 10 kg / mm ^2.
It is 5 kg / mm ² . If the breaking strength is too low, the adhesive tape may be broken when used. If the breaking strength is too high, workability may deteriorate.

The stress relaxation rate is 40% or more, preferably 5%.
0% or more, more preferably 70% or more. If the stress relaxation rate is less than 40%, the workability decreases. The values of the initial elastic modulus, the breaking strength, and the stress relaxation rate can be controlled by, for example, selecting and adjusting the types and proportions of the constituent monomers of the (meth) acrylic polymer constituting the sheet.

A (meth) acrylic polymer composition constituting a film substrate [(meth) acrylic polymer alone,
Or a mixture obtained by adding various additives to a (meth) acrylic polymer] has a glass transition temperature (Tg) of, for example, −2.
The temperature is 0 ° C or higher, preferably -20 ° C to 100 ° C, and more preferably about -15 ° C to 70 ° C. Here, Tg is the temperature at the peak value of G '' (loss modulus) at a frequency of 1 Hz in the dynamic viscoelastic spectrum in the shear direction. When the Tg is lower than -20 ° C, it is difficult to obtain sufficient strength (initial elastic modulus, breaking strength) as a film substrate. If the Tg is too high, good workability may not be obtained.

The (meth) acrylic polymer includes one or more (meth) acrylates as a main monomer component, a nitrogen-containing monomer, a monomer having an acidic group, a vinyl ester such as vinyl acetate, and ethylene. (Meth) acrylic copolymers obtained by copolymerizing olefins such as propylene and olefins and aromatic vinyl compounds such as styrene and α-methylstyrene as appropriate comonomers; polymer alloys obtained by mixing polymers of these monomers; Is used.

The (meth) acrylic acid ester has the general formula (1) CH ₂ ＣC (R ¹ ) COOR ² (1) (wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group. ) Are included. The number of carbon atoms of the alkyl group in R ² is 1 or more, preferably 1 to
14, more preferably about 1 to 10 (especially 1 to 4). The alkyl group may include a hydroxyl group, an ether group, an ester group, an epoxy group, and the like.

Representative examples of the (meth) acrylate represented by the general formula (1) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylate. ) Butyl acrylate,
Examples thereof include isobutyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. The (meth) acrylates may be used alone or in combination of two or more.

[0016] The nitrogen-containing monomers are, for example, the general formula _{(2) CH 2 = C (} R 3) CONR 4 R 5 (2) ( wherein, R ³ represents a hydrogen atom or a methyl group, R ⁴ and R ⁵ are the same or different and each represent a hydrogen atom or an alkyl group, or may be bonded to each other to form a heterocyclic ring with an adjacent nitrogen atom).
Examples include acrylamides, acrylonitrile, vinyl compounds having a nitrogen-containing heterocycle, and amino group-containing (meth) acrylates.

Specific examples of the (meth) acrylamides represented by the formula (2) include, for example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N,
N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, (meth) acryloylmorpholine, diacetone (meth) acrylamide, N-methylol (meth) acrylamide and the like can be mentioned. Examples of the vinyl compound having a nitrogen-containing heterocyclic ring include vinylpyridines such as 4-vinylpyridine.
Examples of the amino group-containing (meth) acrylate include 2- (N, N-dimethylamino) ethyl (meth) acrylate and 3- (N, N-dimethylamino) propyl (meth) acrylate. .

As the monomer having an acidic group, for example, a carboxyl group (including an acid anhydride group),
Examples include monomers containing a phosphoric acid group, a phosphorous acid group, a sulfuric acid group, a sulfurous acid group, a phenolic hydroxyl group, and the like. Representative examples of the monomer having such an acidic group include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid,
2- (meth) acryloyloxyethyl phthalic acid, 2-
(Meth) acryloyloxyethyl acid phosphate, 2-sulfoethyl (meth) acrylate and the like can be mentioned.

Preferred (meth) acrylic polymers are:
It contains a nitrogen-containing monomer and a monomer having an acidic group as a comonomer component. From such a (meth) acrylic polymer, a (meth) acrylic sheet having more balanced physical properties can be obtained by the acid / base molecular interaction. The compounding amount of the nitrogen-containing monomer and the monomer having an acidic group is about 2 to 30% by weight, preferably about 5 to 30% by weight, and more preferably about 5 to 25% by weight, based on the total amount of the monomers.

When a (meth) acrylic polymer is obtained by photopolymerization, as a monomer component, 1,3-butanediol di (meth) acrylate and 1,4-butanediol (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, Pentaerythritol tri (meth) acrylate,
A polyfunctional (meth) acrylate monomer such as dipentaerythritol hexa (meth) acrylate may be blended. The compounding amount of the polyfunctional (meth) acrylate monomer is, for example, about 0.05 to 5% by weight, preferably about 0.1 to 5% by weight, and more preferably about 0.2 to 2% by weight based on the total amount of the monomers. It is.

The film substrate of the present invention may contain, if necessary, various known or commonly used additives such as an antioxidant, an ultraviolet absorber, a coloring agent, a filler, a flame retardant, and an antistatic agent. it can. These additives are used in usual amounts depending on the type.

The production of the film substrate of the present invention is carried out by, for example,
A method of casting a polymer solution obtained by solution polymerization and evaporating a solvent to form a film, a monomer solution, or a monomer-polymer mixture obtained by polymerizing a monomer to some extent and adding a polyfunctional (meth) acrylate monomer as necessary. The method can be performed according to a known or common method such as a method of applying or casting a liquid on a flat surface and forming a sheet by photopolymerization (curing). Especially the method using photopolymerization,
Solvent-free and useful. For photopolymerization, a conventional photopolymerization initiator can be used. The thickness of the film substrate of the present invention is not particularly limited, and can be appropriately set depending on the purpose. Generally, the thickness is 5 to 500 μm, preferably 10 to 20 μm.
It is about 0 μm.

[0023]

The film substrate for an adhesive tape of the present invention comprises:
It has extremely good stress relaxation properties, and exhibits good adhesiveness without floating especially when bonding to a curved surface portion or during press working, and also has excellent weather resistance.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” means “parts by weight”.

Example 1 An acrylic monomer was placed in a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, an ultraviolet irradiation device, and a stirring device.
40 parts of methyl acrylate, 40 parts of ethyl acrylate
Part, acrylic acid 10 parts, N, N-dimethylacrylamide 10 parts, 2,2-dimethoxy-2 as a photopolymerization initiator
0.07 parts of phenylacetophenone was added and photopolymerized to obtain a polymer-monomer mixture having a conversion of 15% by weight. To this mixture, 0.4 part of trimethylolpropane triacrylate was added to 100 parts of the solid content of the mixture to give a syrup. This syrup is applied on a release-treated polyester film having a thickness of 25 μm so as to have a cured thickness of 100 μm, and then cured by irradiating ultraviolet rays to obtain an initial elastic modulus of 11.7 kg.
/ Mm ² , breaking strength: 2.2 kg / mm ² , stress relaxation rate:
An acrylic sheet with 94% Tg: 27 ° C. was obtained.

Example 2 30 parts of methyl acrylate as an acrylic monomer,
30 parts of ethyl acrylate, 20 parts of acrylic acid, N, N
Example 1 except that 20 parts of dimethylacrylamide were used
According to the initial elastic modulus: 34.3kg / mm ^2, the breaking strength: 3.3 kg / mm ^2, the stress relaxation ratio: 85%, Tg:
A 56 ° C. acrylic sheet was obtained.

Example 3 60 parts of ethyl acrylate as an acrylic monomer,
Acrylic acid 20 parts, N, N-dimethylacrylamide 2
Except that 0 part was used, the initial elastic modulus was 8.
An acrylic sheet having 6 kg / mm ² , breaking strength: 1.0 kg / mm ² , stress relaxation rate: 89%, and Tg: 5 ° C. was obtained.

Comparative Example 1 As an acrylic monomer, 50 parts of methyl acrylate was used.
Initial elastic modulus: 0.03 kg / mm ² , breaking strength: according to Example 1, except that 50 parts of ethyl acrylate were used.
0.12 kg / mm ² , stress relaxation rate: 34%, Tg: −
An acrylic sheet at 35 ° C. was obtained.

Comparative Example 2 Thickness: 100 μm, Initial elastic modulus: 39.5 kg / m
m ² , breaking strength: 4.0 kg / mm ² , stress relaxation rate 65
%, Tg: a vinyl chloride sheet at 0 ° C. was used as Comparative Example 2.

Comparative Example 3 Thickness: 60 μm, Initial elastic modulus: 25.2 kg / mm ² ,
Breaking strength: 2.1 kg / mm ² , stress relaxation rate 38%, T
g: Comparative Example 3 using a low-density polyethylene sheet at -125 ° C
And

Comparative Example 4 Thickness: 40 μm, Initial elastic modulus: 55.0 kg / mm ² ,
Breaking strength: 6.1 kg / mm ² , stress relaxation rate 33%, T
g: Comparative Example 4 was a polypropylene sheet at -10 ° C.

Evaluation Test The following tests were performed on the sheets obtained in the examples and comparative examples. (Processability test) An acrylic adhesive (60 parts of ethyl acrylate, 2-ethylhexyl acrylate 4)
0 part, 5 parts of hydroxyethyl acrylate, and 5 parts of tolylene diisocyanate) to form a pressure-sensitive adhesive tape having a thickness of 5 μm. This adhesive tape is applied to SUS304BA (0.4 mm thick),
15 mm drawing (20 mm square tube drawing) was performed with a 0t press, and the state of floating of the adhesive tape after 3 hours was visually observed. The case where no lifting was observed was evaluated as “○”, the case where slight lifting was observed was evaluated as “△”, and the case where floating was clearly observed was evaluated as “×”. (Weather resistance test) W. M. (Sunshine weather meter, black panel temperature: 63 ° C) 5
After exposure for 00 hours, the degree of deterioration of each sheet was visually observed. The case where no deterioration was observed was evaluated as “○”, the case where deterioration was observed in the surface layer portion was evaluated as “△”, and the case where the whole was deteriorated was evaluated as “×”.

Table 1 shows the results.

[Table 1] As shown in Table 1, the (meth) acrylic sheets of the examples have excellent stress relaxation properties, show good workability, and also have excellent weather resistance. Therefore, it turns out that it is extremely useful as a film base material for adhesive tapes.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Sano 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Hiroshi Sugawa 1-1-2, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Katsuya Oji 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4F213 AA21 AA21L WA03 WA53 WA62 WA87 WB01 WC02 4J040 JA09 JB09

Claims (3)

[Claims] 1. A (meth) acrylic polymer,
Initial elastic modulus of 0.5 kg / mm ² or more, breaking strength of 1 k
g / mm ² or more and a stress relaxation rate of 40% or more. 2. The glass transition temperature (Tg) of the (meth) acrylic polymer composition constituting the film substrate is -20.
The film substrate for a pressure-sensitive adhesive tape according to claim 1, which is at least 0C. 3. The adhesive tape film substrate according to claim 1, wherein the (meth) acrylic polymer contains a nitrogen-containing monomer and a monomer having an acidic group as constituent monomers.