JP2002307519A - Acrylic film manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing an acrylic film of good quality at a low cost by extrusion molding. SOLUTION: A powder (A) with a mean particle size of 500 μm or more based on an acrylic resin and a thermoplastic polymer (B) are supplied to a single-screw extruder to be kneaded and the resulting kneaded mixture is subjected to extrusion molding to manufacture the acrylic film. The thermoplastic polymer (B) contains a methyl methacrylate unit as a main component and the reduced viscosity (measured using a solution of 0.1 g of the polymer in 100 ml of chloroform at 25 deg.C) thereof is 0.2-2 l/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic film having excellent film forming properties and appearance by extrusion at low cost.

[0002]

2. Description of the Related Art An acrylic film is usually produced by a melt extrusion method using a single screw extruder. Here, pellets are usually supplied to the extruder as a raw material.

If a powder having a small particle diameter obtained industrially by emulsion polymerization or suspension polymerization is used instead of the pellets, it becomes difficult to stably supply the powder to an extruder, and a film having a uniform thickness cannot be produced. Furthermore, since optical distortion is likely to occur in the film and kneading is likely to be insufficient,
Fish eyes are likely to occur.

When a twin-screw extruder is used in place of the single-screw extruder, the supply of the raw materials to the extruder is relatively stable, but the pressure required for film production cannot be reached at the die portion, and the molten material is melted. Since the supply of resin to the die is not quantitative,
Stable film production cannot be performed.

[0005] From the above, as described above, an acrylic film is produced by using a pellet as a raw material by a melt extrusion method using a single screw extruder. In addition, a process of manufacturing pellets from a resin material is required. The production of the pellets is usually performed by granulating the resin material into pellets using an extruder or the like. In other words, if pellets are used as a raw material, at least a pellet manufacturing step will be added in the production of an acrylic film, and costs for equipment, labor, packaging, transportation, energy, etc. will be required. become.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a good quality acrylic film at low cost by extrusion.

[0007]

According to the present invention, there is provided a single-screw extruder comprising a composition comprising a powder (A) having an average particle diameter of 500 μm or more and composed mainly of an acrylic resin, and a thermoplastic polymer (B) shown below. , Kneading and extruding to form a film.

The thermoplastic polymer (B) has a methyl methacrylate unit as a main component and a reduced viscosity (0.1 g of a polymer is dissolved in 100 ml of chloroform,
(Measured in ° C.) of 0.2 to 2 l / g.

[0009]

Preferred embodiments of the present invention will be described below.

[0010] The acrylic resin used in the present invention is not particularly limited, but preferably has high flexibility and transparency from the viewpoint of workability at the time of production and post-processing, handleability, design and deepness. For example, Japanese Patent Publication No. Sho 62-19309,
Acrylic resin-based multilayered polymers and compositions thereof described in JP-A-63-20459 and JP-A-63-77963 can be used.

Specifically, as the acrylic resin, the innermost layer polymer obtained by using a monomer containing an alkyl acrylate and / or an alkyl methacrylate and a graft crosslinking agent, an alkyl acrylate and, if necessary, a polyfunctional monomer Crosslinked elastic polymer (intermediate layer) obtained by using a monomer containing a polymer and a graft-crosslinking agent, and acrylic having a basic structural unit of an outermost layer polymer obtained by using a monomer containing an alkyl methacrylate A resin-based multilayer structure polymer or the like can be used. As the acrylic resin-based multilayer structure polymer, one kind may be used alone, two or more kinds of multilayer structure polymers may be used in combination, or another resin may be used in combination.

An acrylic resin-based multilayer structure obtained by polymerizing a monomer containing a methacrylate ester in the presence of an elastic copolymer obtained from a monomer containing an acrylic ester and a crosslinkable monomer. A polymer (rubber-containing polymer) can also be used. The acrylic resin-based multilayer structure polymer may be used singly, may be used in combination of two or more multilayer structure polymers, or may be used in combination with another resin.

In the present invention, such an acrylic resin is used as a raw material as powder. Therefore, it is possible to omit the pellet manufacturing process as in the prior art, and to realize cost reduction.

However, this powder (A) must have an average particle diameter of 500 μm or more. If the average particle size is less than 500 μm, the supply to the extruder becomes unstable, and an acrylic film having a uniform thickness cannot be stably manufactured. Even if the average particle diameter is large, there is no problem in production, and the upper limit of the particle diameter is not particularly defined.
However, it is difficult to produce a powder having a large particle diameter. In addition, large particles can be obtained by sieving, but processing costs are high.

The average particle size is a value calculated by sieving for 30 minutes using an M-2 type micro-type electromagnetic vibration sieve manufactured by Tsutsui Chemical Chemical Co., Ltd.

Acrylic resins such as an acrylic resin-based multi-layer polymer having a specific average particle diameter are also available as commercial products.

The thermoplastic polymer (B) used in the present invention
Has a methyl methacrylate unit as a main component.

The reduced viscosity (0.1 g of the polymer dissolved in 100 ml of chloroform and measured at 25 ° C.) is 0.2 to 2
1 / g.

The thermoplastic polymer (B) is a component (processing aid) that plays an important role in suppressing the generation of fish eyes. The reduced viscosity of the thermoplastic polymer is important. It is necessary that the reduced viscosity is 0.2 l / g or more from the viewpoint of suppressing the generation of fish eyes in the obtained acrylic film. On the other hand, if it exceeds 2 l / g, the thermoplastic polymer (B) It is not preferable because fish eyes derived from poor dispersion frequently occur. Particularly preferred reduced viscosity of the thermoplastic polymer (B) is in the range of 0.2 to 1.2 l / g.

In the thermoplastic polymer (B), the content of the methyl methacrylate unit is preferably at least 50% by mass in the thermoplastic polymer (B).

The thermoplastic polymer (B) can contain a vinyl monomer copolymerizable with methyl methacrylate as a copolymer component. The content is thermoplastic polymer (B)
The content is preferably less than 50% by mass.

In the thermoplastic polymer (B) used in the present invention, examples of vinyl monomers copolymerizable with methyl methacrylate include aromatic vinyl compounds, vinyl cyanide compounds, and alkyl (meth) acrylates other than methyl methacrylate. Can be used. Examples of the aromatic vinyl compound include styrene, α-substituted styrene, nucleus-substituted styrene and derivatives thereof, for example, α-methylstyrene, chlorostyrene, vinyltoluene and the like.

Examples of the vinyl cyan compound include acrylonitrile and methacrylonitrile.

Examples of the alkyl (meth) acrylate other than methyl methacrylate include butyl methacrylate and butyl acrylate.

The thermoplastic polymer (B) used in the present invention
Is preferably obtained by an emulsion polymerization method. The method for recovering the emulsified latex of the thermoplastic polymer (B) is not particularly limited. Specific examples include salting out or acid precipitation coagulation, spray drying, freeze drying and the like, and the powder can be collected.

In the present invention, the melt viscosity is improved by blending the thermoplastic polymer (B) with the powder (A) having an average particle diameter of 500 μm or more containing an acrylic resin as a main component, so that the moldability is improved. It is possible to obtain a film which is improved and has less fish eyes. Thermoplastic polymer (B)
Is 0.1 to 20 parts by mass per 100 parts by mass of the powder (A).
Parts by weight are preferred. When the amount of the thermoplastic polymer (B) is less than 0.1 part by mass, the effect of suppressing the generation of fish eyes tends to be insufficient. When the amount is 20 parts by mass or more, the melt viscosity increases and the film formability tends to decrease. It is in.

Further, it is preferable that the lower limit is 1 part by mass and the upper limit is 5 parts by mass.

The method for supplying the thermoplastic polymer (B) of the present invention to a single screw extruder is not particularly limited. The number of fish eyes in the acrylic film obtained by quantitatively supplying the powder (A) having a particle diameter of 500 μm or more to a single screw extruder can be suppressed.

As a specific example of the supply of the thermoplastic polymer (B) to the single-screw extruder, a thermoplastic polymer (B) produced by emulsion polymerization or suspension polymerization is mainly composed of an acrylic resin. A method in which the masterbatch pellets containing the thermoplastic polymer (B) are weighed, mixed and supplied together with the powder (A) having an average particle diameter of 500 μm or more, and the powder having an average particle diameter of 500 μm or more containing acrylic resin as a main component. (A)
And a method of metering, mixing and supplying. Among them, a method using a masterbatch pellet containing the thermoplastic polymer (B) as a raw material is particularly preferable because it can suppress the occurrence of optical distortion of the obtained acrylic film.

Here, the optical distortion means a streak-like or annual ring-like fluctuation occurring on the film surface and inside the film. Optical distortion in acrylic film is, for example, "Functional film technology and application"
[CMC Co., Ltd. issued on July 30, 1982] 1
As described on page 28, when the film is used as a window glass to be used by being bonded to a window glass, it appears as a distortion of an image of the outside world seen through the glass and is important from the viewpoint of external visibility. Generally, the optical distortion of the film is difficult to numerically evaluate as described in the above-mentioned literature,
The evaluation can be made based on the magnitude of the distortion of the external image viewed through the film from a specific angle.

The master batch pellets can be produced by kneading and extruding an acrylic resin and a thermoplastic polymer (B). For kneading and extrusion, a single screw extruder or a twin screw extruder can usually be used. The content of the thermoplastic polymer (B) in the masterbatch pellet is preferably 0.1 to 30 parts by mass based on 100 parts by mass of the acrylic resin. When the amount of the thermoplastic polymer (B) is less than 0.1 part by mass, the amount of the thermoplastic polymer (B) in the acrylic film obtained by using a master batch pellet containing the thermoplastic polymer (B) as a raw material Is insufficient,
The effect of suppressing fish eye generation tends to be insufficient, and if it exceeds 30 parts by mass, the melt viscosity increases, so that the kneadability of the master batch pellets decreases, and the gloss of the acrylic film manufactured using this as a raw material decreases. It tends to decrease.

The acrylic resin used in the production of the masterbatch pellets is not particularly limited, but a powder having an average particle diameter of 500 μm or more and containing the above-mentioned acrylic resin as a main component, which is used in producing the acrylic film. Use of (A) is preferred.

In the masterbatch pellets, a compounding agent for imparting various properties to the acrylic film obtained by the method of the present invention, for example, a stabilizer, an ultraviolet absorber, a processing aid, a plasticizer, an impact resistance Agents, foaming agents, fillers, coloring agents, matting agents, release agents, antibacterial agents, and the like.

When the masterbatch pellets are used, the amount of the masterbatch pellets is not particularly limited.
It is preferably at least 1 part by mass with respect to parts by mass. When the amount of the masterbatch pellet is less than 1 part by mass, optical distortion tends to occur in the acrylic film. It is more preferably at least 5 parts by mass, and even more preferably at least 7 parts by mass. In addition, when the amount of the masterbatch pellets is large, the cost and energy required for shaping are both increased.

In the present invention, it is desirable that the powder (A) containing an acrylic resin as a main component and having an average particle diameter of 500 μm or more is dried with a dryer to a moisture content of 0.3% or less. Acrylic resin has a hygroscopic property, and when the moisture content exceeds 0.3%, defects such as foaming, generation of die, and die lines tend to occur during film production. The moisture content of this powder is
This is a value calculated by heating 10 g of a powder at 120 ° C. until a constant weight is reached and reducing the mass.

The drying method is not particularly limited, and examples thereof include dehumidifying air drying, hot air drying, vacuum drying, and drying using electromagnetic waves. Of the drying methods described above, drying methods other than dehumidifying air drying generally employ a batch drying method using a plurality of dryers, so that continuous drying is difficult. On the other hand, dehumidifying air drying is advantageous for continuous production because it can be dried continuously, and is preferable in terms of equipment space, equipment cost, and the like.
In addition, it is preferable to install a rotary valve or a bridge breaker at the outlet of the dryer.

FIG. 1 is a schematic sectional view illustrating a continuous dehumidifying dryer using dry air. This continuous dehumidifying dryer 1
Has an air heater 2 provided on the dry air introduction side of the apparatus body, a cyclone 3, and a raw material suction hopper 4 communicating with the suction blower side, and further has a raw material discharge side (metering mixer side). A bridge breaker 5 and a rotary valve 6 are provided. By using such a dryer 1, good continuous drying can be performed.

After the powder (A) containing acrylic resin as a main component and having an average particle diameter of 500 μm or more is made to have a water content of 0.3% or less by the above-described drying step, the powder is fed to a single screw extruder. The mixture is supplied, kneaded, and extruded to form a film.

This extrusion molding step may be any method in which the supplied powder is melt-kneaded and extruded into a film. For example, various conventionally known melt extrusion molding methods such as a T-die method and an inflation method may be used. Method can be used. In particular, the T-die method is preferred from the viewpoint of production stability. The single-screw extruder is not particularly limited, but it is preferable to select a screw formation in consideration of kneading properties.

In the production of this acrylic film, if necessary, in addition to the powder (A) having an average particle diameter of 500 μm or more, which is mainly composed of an acrylic resin, and the thermoplastic polymer (B), if necessary, an ultraviolet absorber , Heat stabilizer, light stabilizer, antioxidant,
Various conventionally known additives such as a lubricant, a processing aid, a matting agent, a dye, and a pigment can be added.

When an additive is used, it is preferable that the powder dried in the drying step is measured and mixed together with the additive, supplied to a single screw extruder, and subjected to an extrusion molding step. The automatic metering and mixing device used may be off-line or in-line. However, the use of an in-line automatic weighing and mixing device eliminates the need for manual labor, enables stable continuous production, and eliminates the need for a buffer tank for stocking the mixture. Is advantageous.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. The number of copies and% in the following Examples
Are all based on mass.

The abbreviations used in the examples are as follows.

SFS: sodium formaldehyde sulfoxylate EDTA: disodium ethylenediaminetetraacetate MMA: methyl methacrylate MA: methyl acrylate BA: n-butyl acrylate BD: 1,3 butylene dimethacrylate AMA: allyl methacrylate St: styrene n-OM : N-octyl mercaptan t-BH: t-butyl hydroperoxide emulsifier (1): water of a mixture of 40% mono (polyoxyethylene nonylphenyl ether) phosphoric acid and 60% di (polyoxyethylene nonyl phenyl ether) phosphoric acid Partially neutralized sodium oxide [trade name: Phosphanol LO5
29 <manufactured by Toho Chemical Co., Ltd.> (Preparation Example 1) Preparation of acrylic resin-based polymer (X) The acrylic resin-based polymer (X) was prepared under the following conditions.

In a polymerization vessel equipped with a cooler, ion-exchanged water 25
After charging 0 parts and raising the temperature to 70 ° C., for 5 parts of ion-exchanged water, 0.48 parts of SFS, 0.4 ppm of ferrous sulfate,
A mixture to which 1.2 ppm of EDTA was added was added all at once. After stirring under nitrogen, MMA 1.6 parts, BA 8 parts, BD 0.4
, AMA 0.1 part, CHP 0.04 part and a mixture consisting of 1.3 parts of emulsifier (1) were charged and the reaction was continued for 60 minutes to complete the polymerization of the innermost layer polymer (A). Subsequently, 1.5 parts of MMA, 22.5 parts of BA, 1.0 part of BD, A
A monomer mixture forming a crosslinked elastic polymer (B) consisting of 0.25 parts of MA was added for 60 minutes and polymerized to obtain a two-layer crosslinked rubber elastic body. In this case, the amount of CHP used for the formation of the polymer (B) is 0.0
It was 5% by mass.

Subsequently, 5 parts of MMA, B
A mixture of 5 parts of A, 0.1 parts of AMA and 0.02 parts of CHP was reacted, and finally, as the outermost layer polymer (C), M
MA 52.25 parts, BA 2.75 parts, n-OM 0.19
And the monomer mixture comprising 0.08 parts of t-BH were reacted to form an outermost layer polymer (C) to obtain a latex of an acrylic resin polymer (X). After coagulating the obtained latex with an aqueous solution of magnesium sulfate, the polymer was washed with a 20-fold amount of pure water, dehydrated, and dried to obtain a powder of an acrylic resin-based polymer (X).

The evaluation was performed as follows.

1. Number of film fish eyes The number of fish eyes in 1 m2 of acrylic film was measured using a high-speed and high-performance surface defect inspection device LSC-100 (manufactured by Mitsubishi Rayon Co., Ltd.). Measure a number of 4 mm x 0.5 mm) or more.

2. Film optical distortion When the acrylic film was viewed through an angle of 45 degrees, the case where the distortion of the external image was small was evaluated as ○, the case where the distortion was slightly large was evaluated as Δ, and the case where the distortion was large was evaluated as x.

<Example 1> As the acrylic resin (B),
The powdery acrylic resin-based polymer (X) obtained in Preparation Example (1) was sieved to obtain a powdery acrylic resin-based polymer (X) having an average particle diameter of 650 μm. This powdery acrylic resin-based polymer is supplied with dry air at 80 ° C. using a continuous dehumidifier / dryer [Triangle manufactured by Tanaka Tekko Co., Ltd.] equipped with the bridge breaker 5 and the rotary valve 6 shown in FIG. The powder was dried so that the residence time of the powder in the dryer became 3 hours or more. The moisture content of the powder after drying is 0.1.
2%.

Next, an automatic weighing and mixing apparatus [Tamaki Co., Ltd.]
Manufactured by Auto Blender], 100 parts of the polymer,
As a thermoplastic polymer (B), Metablen P-551A manufactured by Mitsubishi Rayon Co., Ltd. (trade name, reduced viscosity: 0.375 l)
/ G) as a UV absorber as a UV absorber.
2 parts of Tinuvin P (trade name) manufactured by Asahi Denka Kogyo Co., Ltd. and 0.3 parts of ADK STAB AO-50 (trade name) manufactured by Asahi Denka Kogyo Co., Ltd. Blender].

This mixture was supplied to a single-screw extruder with a 1000 mm width T die [P-65, manufactured by Nippon Steel Works Co., Ltd.], kneaded, extruded from the T die, and having a uniform thickness of 50 μm in average thickness. An acrylic film was obtained. The extrusion conditions at this time were: cylinder set temperature 220 ° C., T-die set temperature 23
0 ° C., screw rotation speed 30 rpm, take-off speed 30
m / hour.

Table 1 shows the results of the number of film fish eyes and the optical distortion of the film.

<Example 2> As the acrylic resin (A),
The powdery acrylic resin-based polymer (X) obtained in Preparation Example (1) was sieved to obtain a powdery acrylic resin-based polymer (X) having an average particle diameter of 800 µm. 100 parts of this acrylic resin-based polymer (X), 3 parts of the thermoplastic polymer (B) used in Example 1, and Asahi Denka Kogyo Co., Ltd.
Copies of ADK STAB LA-31 (trade name) made by HAL
A: Adekastab LA-57 manufactured by Asahi Denka Kogyo Co., Ltd.
The same method as in Example 1 (after drying) except that 0.5 part (trade name) and 0.3 part ADK STAB AO-50 (trade name, manufactured by Asahi Denka Kogyo KK) were used as the antioxidant. An acrylic film having a uniform film thickness with an average thickness of 50 μm was obtained at a powder moisture content of 0.2%.

Table 1 shows the results of the number of film fish eyes and the optical distortion of the film.

Example 3 100 parts of the powdery acrylic resin-based polymer (X) used in Example 1 and 20 parts of the thermoplastic polymer (B) used in Example 1 were used in Example 1. 1 part of antioxidant was added to twin screw extruder [Nippon Steel Works Co., Ltd., TEX
-44] to obtain a master batch pellet. Extrusion conditions at this time were a cylinder set temperature of 220 ° C., a die set temperature of 230 ° C., a screw rotation speed of 30 rpm, and a take-up speed of 30 m / hour.

20 parts of the obtained pellets, 100 parts of the acrylic resin polymer (X) used in Example 1, 3 parts of the ultraviolet absorbent used in Example 2, and 0.5 part of HALS were mixed. An acrylic film having an average thickness of 50 μm and a uniform thickness was obtained in the same manner as in Example 1 (water content of the dried powder was 0.2%).

Table 1 shows the results of the number of film fish eyes and the optical distortion of the film.

<Example 4> 20 parts of the masterbatch pellets used in Example 3, 100 parts of the acrylic resin polymer (X) used in Example 1, and Tinuvin 1577 (manufactured by Ciba Geigy) as an ultraviolet absorber. Was mixed in the same manner as in Example 1 (moisture percentage of powder after drying was 0.2%) to obtain an acrylic film having an average thickness of 50 μm and a uniform thickness.

Table 1 shows the results of the number of film fish eyes and the optical distortion of the film.

Comparative Example 1 100 parts of the powdery acrylic resin-based polymer (X) used in Example 1, 2 parts of the ultraviolet absorber used in Example 1, and 0.3 part of the antioxidant An acrylic film having an average thickness of 50 μm and a uniform film thickness was obtained in the same manner as in Example 1 (water content of the dried powder was 0.2%) except that it was used.

Table 1 shows the results of the number of film fish eyes and optical distortion of the film.

Comparative Example 2 The powdery acrylic resin-based polymer (X) used in Example 1 was sieved to give an average particle diameter of 450.
A μm powder was obtained. 100 parts of this powder, 3 parts of the thermoplastic polymer (B) used in Example 1, 2 parts of the ultraviolet absorber used in Example 3, and 0.3 part of the antioxidant used in Example 1 Except for using it, an attempt was made to produce an acrylic film having an average thickness of 50 μm in the same manner as in Example 1 (water content of the dried powder was 0.2%). No further evaluation was possible. Comparative Example 3 The powdery acrylic resin-based polymer (X) used in Example 1 and one part of the antioxidant used in Example 1 were mixed with a twin-screw extruder [TEX-, manufactured by Nippon Steel Works, Ltd.] 44], and pellets were obtained in the same manner as in Example 4.

20 parts of the obtained pellets were mixed with 100 parts of the acrylic resin-based polymer used in Example 1, 3 parts of the ultraviolet absorbent used in Example 2 and 0.5 part of HALS. An acrylic film having an average thickness of 50 μm and a uniform thickness was obtained in the same manner as in Example 1 (water content of the dried powder was 0.2%).

Table 1 shows the results of the number of film fish eyes and the optical distortion of the film.

[0066]

【table 1】

[0067]

As described above, according to the method for producing an acrylic film of the present invention, a high-quality acrylic film having a small number of fish eyes, a uniform thickness and a conventionally known pellet is used as a raw material. It can be manufactured at a lower cost than the conventional manufacturing method. In addition, by using masterbatch pellets containing certain thermoplastic polymerizations,
The optical distortion of the obtained film can be suppressed, and it can be used in the field where various optical characteristics are required, and its industrial value is extremely high as a method for producing a high-quality and low-cost optical film.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a continuous dehumidifying dryer using dry air.

[Explanation of symbols]

 Reference Signs List 1 dryer 2 air heater 3 cyclone 4 raw material suction hopper 5 bridge breaker 6 rotary valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 33:00 B29K 33:00 B29L 7:00 B29L 7:00 F term (Reference) 4F070 AA32 AB08 AB09 AC83 AE13 FA01 FA17 FB03 FC05 4F071 AA33 AA77 AA88 AD02 AF29 BA01 BB06 BC01 4F207 AA21 AB02 AB06 AB07 AB11 AB12 AB14 AC08 AG01 KA01 KA17 KL84 4J002 BG062 BN121 FA081 GP00

Claims (2)

[Claims] 1. A single-screw extruder is supplied with a powder (A) having an acrylic resin as a main component and having an average particle diameter of 500 μm or more and the following thermoplastic polymer (B), and kneaded and extruded to form a film. A method for producing an acrylic film, which comprises molding. Thermoplastic polymer (B) Methyl methacrylate unit as a main component, reduced viscosity (0.1 g of polymer dissolved in 100 ml of chloroform,
(Measured in ° C.) of 0.2 to 2 l / g. 2. The method for producing an acrylic film according to claim 1, wherein the thermoplastic polymer (B) is supplied as a masterbatch pellet with the powder (A) to a single screw extruder.