JP2000109575A - Acrylic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylic resin film hardly causing whitening when folded, excellent in impact resistance, transparency and designing properties, and useful for surface-layered member by regulating the film so as to be composed of a composition comprising an acrylic resin and an acrylic elastic particles, and so as to have a value not less than a specific value of a prescribed heat shrinkage. SOLUTION: This acrylic resin film comprises (A) an acrylic resin such as a mixture of one or more kinds of acrylic polymers having 70,000-200,000 weight average molecular weights, with one or more kinds of acrylic polymers having >200,000 weight average molecular weights, or the like, preferably in an amount of >=50 pts.wt. (based on 100 pts.wt. total of the components A and B), and (B) acrylic elastomer particles of acrylic polymers with multilayered structures including rubbery elastic layers, or the like, (preferably having 50-500 nm particle diameters), preferably in an amount of <=50 pts.wt., and has >=5%, preferably >=20% heat shrinkage in the direction showing the maximum heat shrinkage in a heat shrinkage test, and <=5% heat shrinkage in the direction crossing to the direction. The thickness of the film is preferably 0.01-0.6 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an acrylic resin film.

[0002]

2. Description of the Related Art Acrylic resin films have been used as surface members of various molded articles, display panels, etc. because of their excellent transparency and surface gloss. However, the conventional acrylic resin film has a problem of low impact resistance.

[0003]

SUMMARY OF THE INVENTION Accordingly, the present inventors
As a result of intensive studies to develop an acrylic resin film with superior impact resistance, the present inventors have found that an acrylic resin film having a specific heat shrinkage ratio has sufficient impact resistance, and the present invention Reached.

[0004]

That is, the present invention comprises a composition of an acrylic resin and an acrylic elastic particle, and has a heat shrinkage of 5% in a direction showing the maximum heat shrinkage in a heat stretching test. It is an object of the present invention to provide an acrylic resin film characterized by having a heat shrinkage of at least 5% in a direction orthogonal to the above direction.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The acrylic resin film of the present invention comprises a composition of an acrylic resin and acrylic elastic particles.

Examples of the acrylic resin include polyalkyl methacrylate, a copolymer of alkyl methacrylate and alkyl acrylate, and the like. As methacrylic acid alkyl esters,
For example, methyl methacrylate, ethyl methacrylate and the like can be mentioned. The alkyl group in the alkyl acrylate is preferably an alkyl group having 2 to 10 carbon atoms. Examples of the alkyl acrylate include acrylates, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, Isobutyl acrylate, hexyl acrylate, octyl acrylate and the like can be mentioned. When a copolymer of alkyl methacrylate and alkyl acrylate is used as the acrylic resin, the alkyl methacrylate unit in the copolymer is 50% by weight or more, preferably 50 to 99% by weight, and the alkyl acrylate unit is Is preferably 50% by weight or less, more preferably 50 to 1% by weight. Further, the acrylic resin may further contain another monomer unit as a copolymer component within a range not to impair the object of the present invention.

As the acrylic resin, a polymer obtained by polymerization may be used as it is, or a mixture of two or more polymers having different weight average molecular weights may be used. Among them, a mixture containing at least one polymer having a weight average molecular weight of 70,000 to 200,000 and at least one polymer having a weight average molecular weight exceeding 200,000 is preferable. It is possible to combine the effects of improving the formability, such as preventing the occurrence of irregularities, and improving the surface hardness in the case of performing thermoforming after forming the film into a film. The weight average molecular weight of a polymer having a weight average molecular weight exceeding 200,000 is usually 700,000 or less. When the weight-average molecular distribution measured by GPC (gel permeation chromatography) is observed on a chart, such a mixture exhibits a form in which the base is widened or a form with a shoulder.

The acrylic elastic particles applied to the composition constituting the acrylic resin film of the present invention are particles made of an acrylic polymer and having rubber elasticity. The acrylic elastic particles may be a single layer or a multilayer acrylic polymer including a rubber elastic layer, but the multilayer acrylic polymer including a rubber elastic layer is
It is preferably used because it becomes an acrylic resin film having excellent transparency.

The multilayer acrylic polymer is an acrylic polymer having a multilayer structure of at least two layers, preferably three layers. For example, the inner layer has an alkyl group having 4 to 4 carbon atoms.
A rubber elastic body made of a copolymer of an alkyl acrylate of 8 and a polyfunctional monomer, and a two-layer acrylic polymer whose outer layer is a hard polymer mainly composed of methyl methacrylate. Among them, the innermost layer is a hard polymer containing methyl methacrylate as a main component, and the intermediate layer is made of a copolymer of an alkyl acrylate having 4 to 8 carbon atoms of an alkyl group and a polyfunctional monomer. A three-layer acrylic polymer in which the outermost layer is a hard polymer containing methyl methacrylate as a main component is preferable.
Such a multilayer acrylic polymer is disclosed in, for example,
It can be produced by the method described in JP-A-27576.

The amount of the acrylic resin and the acrylic elastic particles used in the composition is usually per 100 parts by weight of the total amount of the acrylic resin and the acrylic elastic particles.
The amount of the acrylic resin used is 50 parts by weight, and the amount of the acrylic elastic particles used is 50 parts by weight or less, but the amount of the acrylic resin used is 95 to 50 parts by weight and the amount of the acrylic elastic particles is The amount used is preferably from 5 to 50 parts by weight, the amount of the acrylic fat used is from 90 to 70 parts by weight, and the amount of the acrylic elastic particles is more preferably from 10 to 30 parts by weight.

The particle size of the acrylic elastic particles is usually 5
The range is about 0 to 500 nm, preferably about 100 to 400 nm, and more preferably about 250 to 350 nm. In general, in a normal acrylic resin film using a multilayer structure acrylic polymer as the acrylic elastic particles, if the particle size of the multilayer structure acrylic polymer is 100 nm or more, it becomes white and transparent when bent. Usually, care must be taken when handling the acrylic resin film, since the acrylic resin film of the present invention has a particle size of 1 μm in the multilayer structure acrylic polymer.
Even if it is 00 nm or more, it does not easily whiten when it is bent, so that it can be handled relatively easily.

The composition applied to the acrylic resin film of the present invention can be easily produced by melt-kneading such an acrylic resin and acrylic elastic particles in the same manner as usual.

The acrylic resin film of the present invention may contain the same additives as those usually used. Examples of such additives include a hindered phenol antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. Weathering agents such as antioxidants, ultraviolet absorbers, hindered amine light stabilizers,
Examples include a flame retardant, a colorant, a pigment, an inorganic filler, and a plasticizer. As the ultraviolet absorber, general benzotriazole-based and benzophenone-based ultraviolet absorbers may be used alone or in combination of two or more. However, from the viewpoint of reducing volatile components from the film, a high-molecular-weight benzo Triazole-based UV absorbers, for example, 2,2-methylenebis [6- (2H-benzotriazol-2-yl)
-4- (1,1,3,3-tetramethylbutyl) phenol] and the like are preferably used. The plasticizer is used for the purpose of optimizing the rigidity and heat resistance of the acrylic resin film. Acid esters and the like. These additives may be added in advance to the acrylic resin, for example, or may be added when the acrylic resin and the acrylic elastic particles are melt-kneaded.

The acrylic resin of the present invention may contain another copolymer as long as the object of the present invention is not impaired.

The acrylic resin film of the present invention has a heat shrinkage rate of 5% or more in a direction showing the maximum heat shrinkage rate in a heat stretchability test and a heat shrinkage rate of 5% or more in a direction perpendicular to the direction. Although it is necessary, the heat shrinkage in the direction showing the maximum heat shrinkage is preferably 20% or more, more preferably the heat shrinkage in the direction showing the maximum heat shrinkage is 20% or more and the maximum. The heat shrinkage in a direction orthogonal to the direction indicating the heat shrinkage is 20% or more. The upper limit of the heat shrinkage is not particularly limited, but is usually about 80% or less. Further, the heat shrinkage rate in the direction showing the maximum heat shrinkage rate and the heat shrinkage rate in the direction orthogonal to the direction may be different from each other or may be almost the same value.

In the heat stretching test, a film was sandwiched between two metal plates and kept at 170 ° C. while being kept horizontal.
By heating for 10 minutes and then cooling. Formula for calculating the heat shrinkage in each direction before and after the test (1) Heat shrinkage (%) = (L ₀ −L) / L ₀ × 100 (1) [where L ₀ is the distance between gauge points before heating. And L indicates the distance between gauge points after heating. ], The direction in which the largest heat shrinkage rate is obtained by heating is determined, and this direction is referred to as “direction indicating the maximum heat shrinkage rate”, and this heat shrinkage rate is referred to as “the heat shrinkage rate in the direction indicating the maximum heat shrinkage rate”. ". By this heating, the heat shrinkage in the direction orthogonal to the direction showing the largest heat shrinkage can be determined at the same time.

During the heating in the heat stretching test, the acrylic resin film should not be prevented from contracting due to the close contact between the acrylic resin film and the metal plate.
Fine particles are preferably dispersed between the metal plate and the film. Here, the fine particles are not particularly limited as long as they do not prevent the acrylic resin film from shrinking. For example, inorganic fine particles such as titanium oxide particles, talc particles, and silicon oxide particles may be used. Commercially available products such as baby powder may be used as such fine particles. As a metal plate,
From the viewpoint of heat transfer, an aluminum plate is preferable, and the weight of a metal plate whose acrylic resin film is used on the upper side is 0.01 to 0.02 g / cm ² per unit area.
It is about. The distance between gauge points (L ₀ ) before heating is usually 100
mm. In addition, a general acrylic resin film may be stretched by heating in a heat stretching test, but in this case, the heat shrinkage calculated by the above equation (1) is calculated as a negative value.

The acrylic resin film having a heat shrinkage ratio specified in the present invention is obtained by, for example, extruding a composition comprising an acrylic resin and acrylic elastic particles by a chill roll, and bringing both surfaces of the film into contact with the roll surface. Extrusion molding method, belt cooling extrusion method in which both surfaces are brought into contact with a metal belt, molding by solvent casting method, etc. to obtain a film, and then stretching the film using a uniaxial tenter or a biaxial tenter A method of forming a composition by inflation extrusion, a method of forming a composition by inflation extrusion to obtain a film, and then stretching the film by using a uniaxial tenter or a biaxial tenter. can do. In the acrylic resin film of the present invention obtained by such a method, usually, the direction parallel or perpendicular to the extrusion direction or the stretching direction is the direction showing the maximum heat shrinkage in the heat stretching test. The thickness of such an acrylic resin film is usually 0.01 to 0.6 mm, preferably 0.03 to 0.3 m.
m.

Since the acrylic resin film of the present invention has excellent impact resistance, it may be used as it is as a surface layer member of various molded products, display panels, etc., or may be used as a multilayer film by laminating with other films. You may. in this case,
The acrylic resin film of the present invention may be used as an outermost layer or an inner layer of a multilayer film. Here, examples of the other film include a vinyl chloride resin film, a polyolefin resin film, a polyvinyl alcohol resin film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polycarbonate film, a norbornene resin film, and the like. Such a multilayer film can be easily manufactured by, for example, a laminating method, a pressing method, or the like.

The acrylic resin film of the present invention is provided with a pressure-sensitive adhesive layer on one side, and is used as a display film (marking film) for exterior / advertising, as well as for simultaneous lamination of injection molding, wallpaper or lamination. Can be used as a film. Further, since it has high impact resistance and high weather resistance of an acrylic resin, it can be used as an agricultural film. In this case, in order to impart anti-fog properties to the film,
It may contain a surfactant, a hydrophilic polymer, an inorganic colloid sol, or the like, or may be applied to the film surface.
By imparting antifouling treatment to the surface of the acrylic resin film of the present invention and bonding it to a plastic plate, it can also be used as a soundproof plate or a lighting cover.

The acrylic resin film of the present invention is suitable as a film for shrink wrapping, which is used as a label for liquid detergents, food bottles, plastic containers and the like, by printing various patterns and characters on one side. In this case, it is preferable that the heat shrinkage in the direction showing the maximum heat shrinkage in the heat stretch test is 20% or more.

[0022]

The acrylic resin film of the present invention has excellent impact resistance, and is therefore useful as a surface layer member for various molded products, display panels, and the like. Further, when the particle diameter is 1
Even when the acrylic polymer having a multilayer structure having a thickness of 00 nm or more is contained, since it is not easily whitened when folded as compared with a conventional acrylic resin film, transparency and design are less likely to be impaired.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The acrylic resin films obtained in the examples were evaluated by the following methods. (1) Heat stretching test From acrylic resin film, a test piece (12 cm × 12
cm) was cut out so that one side thereof was parallel or orthogonal to the extrusion direction. This test piece was placed on two aluminum plates [40 cm × 40 cm, thickness 0.5 mm,
Weight per unit area 0.013 g / cm ² ]. In addition, between the test piece and the aluminum plate, fine particles ("Johnson Baby Powder", manufactured by Johnson & Johnson Co., Ltd.) were scattered. Next, the test piece was heated in a 170 ° C. oven for 10 minutes while being kept horizontal in a state of being sandwiched between aluminum plates to perform a heat shrinkage test. The heat shrinkage measured using two points on a straight line parallel to the extrusion direction of the acrylic resin film passing through the center of the test piece as a reference point is defined as the heat shrinkage in the longitudinal direction, and the acrylic resin passes through the center of the test piece. The heat shrinkage measured using two points on a straight line parallel to the width direction of the film as a score was defined as the heat shrinkage in the transverse direction. The heat shrinkage in the vertical direction and the heat shrinkage in the horizontal direction before and after heating were calculated by the above equation (1). Note that inter-gauge length L ₀ before heating is 100 mm. (2) Surface hardness Pencil hardness was measured according to JIS K5400. (3) Impact resistance The pendulum impact strength was measured by the following method. Using a pendulum impact tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.), an impact ball (25 mmφ)
Using a hemisphere) was used to determine the breaking energy when the impact ball pierced the center of the 50 mmφ impact surface. (4) Bending whitening The acrylic resin film is folded in two, a load of 1.5 kg is applied, the state is maintained for 30 seconds in a state of being folded, then the film is opened by removing the load, and a change in a part of a bending line caused by bending is performed. Was visually observed and evaluated according to the following criteria. ：: No whitening was observed at the bent line portion Δ: Whitening was slightly observed at the bent line portion ×: Whitened was observed at the bent line portion

Comparative Example 1 30 parts by weight of a powder of polymethyl methacrylate (weight average molecular weight 120,000), a butyl acrylate-methyl methacrylate copolymer [butyl acrylate unit 20% by weight, methyl methacrylate unit 80% by weight, Weight average molecular weight 300,000] 5
Acrylic polymer having a three-layer structure including 0 parts by weight and a spherical rubber elastic layer [the innermost layer: methyl methacrylate or a copolymer, the middle layer: a soft rubber elastic body containing butyl acrylate as a main component, the outermost layer : Polymethyl methacrylate, average particle diameter 300 nm] (see Example 3 of Japanese Patent Publication No. 55-27576) 20 parts by weight were melt-kneaded to obtain an acrylic resin composition, which was pelletized by a twin-screw extruder. The pellets of the acrylic resin composition were extruded through a T-die (set temperature: 250 ° C.) using a single-screw extruder of 65 mmφ, and cooled so that both surfaces were completely in contact with a polishing roll. Film (thickness 0.13
mm). This acrylic resin film had the largest heat shrinkage in the longitudinal direction (extrusion direction). Table 1 shows the evaluation results. In addition, when the surface of this acrylic resin film was observed by FE-SEM, [Pt-Pd evaporation,
Acceleration voltage: 3 kV, sample current: 10 μA, magnification: 100
00 times], and had a smooth surface shape.

Example 1 The film obtained in Comparative Example 1 was stretched in a transverse direction (direction orthogonal to the extrusion direction in Comparative Example 1, width direction) using a uniaxial tenter [stretching temperature 100 ° C., stretching ratio 3 times, stretching speed 8.6 m / min], and an acrylic resin film (0.04 mm in thickness) was obtained. This acrylic resin film had the largest heat shrinkage in the horizontal direction (width direction).
Table 1 shows the evaluation results. The surface of the acrylic resin film was observed by FE-SEM [Pt-Pd deposition, acceleration voltage: 3 kV, sample current: 10 μA, magnification: 1]
0000 times], it had an uneven surface shape. AFM observation (Digital Instrument)
Mens NanoScope IIIa, scanning range:
10 μm square, scanning speed: 0.3 Hz, room temperature, in the air), and the roughness of the unevenness was measured according to JIS B0601-1982, and Ra (center line average roughness) was 2.394.
nm, Rmax (maximum height) is 42.136 nm, Rz
(Ten-point average roughness) was 23.433 nm (JIS).
B0601-1982).

Example 2 The film obtained in Example 1 was wound around a paper tube (diameter: 30 mm) and heated at 100 ° C. for 1 minute. This acrylic resin film can be used as a shrink wrapping film.

[0027]

[Table 1] 加熱 Heat shrinkage (%) Thickness Impact resistance Bending whitening Pencil hardness Vertical direction Horizontal direction (mm) (kgcm) ────────────────────────────────── ── Comparative Example 1 50 -10 0.13 1 × HB Example 1 50 65 0.044 ○ B ───────────────────────── ───────────

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masakazu Yokoyama 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Co., Ltd. F-term (reference) 4F071 AA33 AA77 AF43 AH04 BA01 BB07 BC01 4J002 BG042 BG051 BN122 GG02 4J026 AA45 AC15 AC18 BA27 FA02 GA09

Claims (9)

[Claims] 1. A composition comprising an acrylic resin and an acrylic elastic particle, wherein a heat shrinkage ratio in a direction showing a maximum heat shrinkage ratio in a heat stretchability test is 5% or more and is orthogonal to the direction. An acrylic resin film having a heat shrinkage in the direction of 5% or more. 2. An acrylic resin having a weight average molecular weight of 70,000 or more.
At least one type of an acrylic polymer that is 200,000;
The acrylic resin film according to claim 1, which is a mixture containing at least one acrylic polymer having a weight average molecular weight of more than 200,000. 3. The acrylic resin film according to claim 1, wherein the acrylic elastic particles are a multilayer acrylic polymer containing a rubber elastic layer. 4. An acrylic polymer having a multilayer structure, wherein the inner layer is a rubber elastic body comprising a copolymer of an alkyl acrylate having an alkyl group having 4 to 8 carbon atoms and a polyfunctional monomer, and the outer layer is formed of a rubber elastic body. A two-layer acrylic polymer, which is a hard polymer mainly composed of methyl methacrylate, or a hard polymer mainly composed of methyl methacrylate as the innermost layer, and the intermediate layer has an alkyl group having 4 to 4 carbon atoms. 8 is a rubber elastic body composed of a copolymer of an alkyl acrylate and a polyfunctional monomer, and the outermost layer is a three-layer acrylic polymer having a hard polymer containing methyl methacrylate as a main component. The acrylic resin film according to claim 3. 5. The acrylic elastomer particles having a particle size of 50 to 50.
The acrylic resin film according to claim 1, which has a thickness of 500 nm. 6. An acrylic elastomer particle having a particle diameter of 100 nm.
The acrylic resin film according to claim 3, which is as described above. 7. The method according to claim 1, wherein the amount of the acrylic resin is at least 50 parts by weight and the amount of the acrylic elastic particles is at most 50 parts by weight per 100 parts by weight of the total amount of the acrylic resin and the acrylic elastic particles. The acrylic resin film according to claim 1. 8. The acrylic resin film according to claim 1, which has a thickness of 0.01 to 0.6 mm. 9. The film for shrink wrapping comprising an acrylic resin film according to claim 1, wherein a heat shrinkage ratio in a direction showing a maximum heat shrinkage ratio in a heat stretchability test is 20% or more.