JPH10264241A - Manufacture of polyester moldings - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve glare proof as the translucent cover of an illuminator by spreading a liquid droplet to a polyester sheet to make a surface temperature non-uniform and thereby reducing the glossness of the surface below a specified level. SOLUTION: When thermally forming a polyester sheet, it is rapidly cooled by spreading a microliquid droplet to the surface to make the surface temperature delicately non-uniform. Thus the surface glossness of moldings is lowered to 90% or less. Polyester is composed of an aromatic dicarboxilic acid component and a glycol component, and terephthalic acid is used as the aromatic dicarboxylic acid. In addition, from the viewpoint of the thickness uniformity and the deep drawing properties of the sheet, the temperature of a casting drum is preferably 0-80 deg.C. Further, the thickness of the polyester sheet is normally 0.05-10 mm, and the spreading of the liquid droplet is preferably performed while the surface temperature of the polyester is as hot as 80 deg.C or higher. In this case, the liquid droplet of 10-500 g/m<3> creates an atomization state.

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 a molded article having a beautiful appearance by thermoforming a polyester sheet. The molded article produced by the method of the present invention has excellent antiglare properties when used as a light-transmitting cover of a lighting fixture.

[0002]

2. Description of the Related Art Conventionally, as a substitute for glass, a molded article of an acrylic resin sheet which is lightweight and highly processable has been used in many fields. One example is a translucent cover of a lighting fixture or an advertising board with a lighting fixture installed inside, and this is partly due to the high quality of the acrylic resin product.

[0003]

However, acrylic resins generally have a problem of poor impact resistance. Also, when used for lighting equipment covers, etc., in order to impart opacity, special processing is applied to the surface of the processing mold, or opacity is previously given to the acrylic resin sheet itself to be subjected to molding. And there is a problem that the manufacturing cost increases. The present invention seeks to solve such a problem.

[0004]

According to the present invention, when a molded article is produced from a polyester sheet by thermoforming, fine droplets are sprayed on the polyester sheet to obtain a temperature distribution finely distributed on the surface of the polyester sheet. A polyester sheet produced through a process of generating a non-uniform state or spraying fine droplets onto a polyester melt-extruded into a sheet while at a high temperature to generate a non-uniform state of temperature. By using this, it is possible to produce a polyester molded product having a beautiful appearance and a high-grade feeling suitable as a substitute for an acrylic resin and having at least one surface having a glossiness of 90% or less.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail. The polyester used in the present invention comprises an aromatic dicarboxylic acid component and a glycol component. Usually, terephthalic acid is mainly used as the aromatic dicarboxylic acid, but 2,6-naphthalenedicarboxylic acid can also be used. Elene glycol is mainly used as the glycol component. In order to improve the physical properties of the polyester, isophthalic acid and other polycarboxylic acids, diethylene glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, propylene glycol, 1,4- Butanediol,
Modification components such as diols such as 1,2-neopentyl glycol and bisphenol A, and hydroxycarboxylic acids such as p-oxyethoxybenzoic acid can also be contained. Usually, polyethylene terephthalate in which the ethylene terephthalate unit accounts for 80% by weight or more, preferably 90 to 99% by weight, is used. When the content of the ethylene terephthalate unit is less than 80% by weight, fusion tends to occur when the pellets are dried, and the bending strength, chemical resistance, weather resistance, etc. of the obtained molded product are reduced. Conversely, when the content of the ethylene terephthalate unit exceeds 99% by weight, the processability in thermoforming the polyester sheet is reduced.

The production of polyester by polymerization of an aromatic dicarboxylic acid component and a glycol component can be carried out by a conventional method. The polymerization has an intrinsic viscosity of 0.5 to 1.3 dl /
Preferably, the reaction is carried out so as to produce g of polyester.
Those having an intrinsic viscosity of less than 0.5 dl / g have mechanical properties,
In particular, not only the impact resistance is poor, but also the appearance of the molded product is poor. Conversely, if the intrinsic viscosity exceeds 1.3 dl / g, the processability becomes poor. A suitable intrinsic viscosity of the polyester used in the present invention is 0.6 to 1.0 dl / g. In the polyester used in the present invention, other resins such as polycarbonate, polyolefin, polyamide and the like may be added to the molded product as long as the desired properties are not impaired. It is preferable to limit the amount of these resins to 30% by weight or less, especially 10% by weight or less. Further, an ultraviolet absorber, an antioxidant, a lubricant, a dye / pigment, a filler and other conventional auxiliaries can be incorporated into the polyester.

In the present invention, polyester is first formed into a polyester sheet. Sheeting may be performed by a conventional method, and usually, a method is employed in which polyester is dried, extruded into a sheet at 200 to 320 ° C. from a melt extruder, and cooled and solidified by contact with a casting drum. In the present invention, in order to improve the uniformity of the thickness of the obtained sheet and the deep drawability at the time of thermoforming, and also to improve the impact resistance of a molded product obtained by molding this sheet,
The temperature of the casting drum is from 0 to 80 ° C, especially from 10 to
The temperature is preferably set to 50 ° C. It is also preferable to combine a nip roll with the casting drum and press the polyester sheet against the casting drum.

The thickness of the polyester sheet is usually 0.0
5 to 10 mm. If it is too thin, the rigidity and impact resistance of the molded product obtained by thermoforming the molded product will be insufficient.
Conversely, if it is too thick, thermoforming becomes difficult. The preferred thickness of the polyester sheet is 0.05 to 5 mm, especially 0.05 to 3 mm.
mm. If desired, a coating layer may be formed on the polyester sheet by a known method to adjust the surface glossiness. That is, in the present invention, it is important that the surface gloss of the obtained molded article is 90% or less,
This is mainly achieved by spraying droplets onto the sheet during sheet formation or thermoforming, which will be described later, but it is also possible to supplementarily utilize means such as formation of a coating layer and blending of fillers in polyester. it can.

In the present invention, the polyester sheet is thermoformed into a molded article having a desired shape. In thermoforming, fine droplets are sprayed on the surface by utilizing the heating of the polyester sheet. As a result, the surface condition is minutely nonuniform, the surface glossiness of the obtained molded article is lowered, and the molded article has a beautiful appearance and a high-grade feel. The spraying of the droplets is preferably performed after heating the polyester sheet. In other words, when fine droplets are sprayed on a heated polyester sheet, the surface portion on which the droplets adhere is rapidly cooled, causing a temperature distribution that is finely distributed on the surface, thereby causing the surface to be finely non-uniform. Be transformed into
The spraying of the droplets has a polyester surface temperature of 80 ° C or higher,
In particular, it is preferable to perform the heating during a heating state of 100 ° C. or higher. Normal temperature water or an aqueous solution may be used as the droplet. The spraying of the droplets may be determined according to a desired surface state, with the aim of creating a spraying state containing droplets of 10 to 500 g / m ³ , preferably 30 to 300 g / m ³ . The spray amount of the droplet may be determined according to the desired surface state, but usually the droplet amount is 20 to 200 g.
/ m ² .

[0010] If desired, the surface can be made non-uniform by a method in which droplets are sprayed and then the polyester sheet is heated. In this case, the temperature of the portion to which the liquid droplets adhere is delayed, so that the temperature of the polyester sheet becomes uneven on the surface. As a further alternative, when a polyester sheet is produced by melt extrusion, droplets can be sprayed on a high-temperature polyester sheet to make the surface non-uniform. In this case, the polyester has a surface temperature of 80 to 150 ° C., preferably 10 to 150 ° C.
It is preferred to spray the droplets while at 0-130 ° C.
The droplets used for spraying and the amount of spraying may be the same as those used for thermoforming. In the case where thermoforming is performed using a polyester sheet whose surface has been made fine and non-uniform as described above, spraying of droplets during thermoforming can be omitted. Of course, droplets may be sprayed during thermoforming if desired. In this case, it is preferable to spray droplets having different sizes in the sheet forming stage and the thermoforming stage,
By doing so, the appearance of the molded article obtained can be made more complicated, and its luxury and beauty can be enhanced.

[0011] The thermoforming itself can be performed by a conventional method. Usually, vacuum forming or pressure forming is performed, but when a large-sized molded product is obtained or when a thick polyester sheet is used, it is preferable to use the plug assist method.

According to the method of the present invention, a molded article having a surface glossiness of 90% or less, preferably 50% or less, having excellent antiglare properties and having a high-quality and beautiful appearance can be easily prepared. Can be manufactured. Moreover, the light transmittance of the obtained molded product is usually 90% or less, and a molded product having a light transmittance of 60 to 90% suitable as a light-transmitting cover for lighting equipment can be easily produced. The molded article produced by the method of the present invention has excellent impact resistance and other mechanical properties and solvent resistance and other chemical properties which are characteristics of polyester. Therefore, the molded article obtained by the method of the present invention can be suitably provided for various uses utilizing these characteristics. Examples of some of the uses include a translucent cover of a lighting fixture and an advertising board having a lighting fixture installed inside.

Conventionally, ground glass, frosted acrylic resin, and the like have been mainly used for these uses. However, glass has a drawback that it is heavy and easily broken, and it is dangerous if broken. Acrylic resin is also liable to be damaged and easily eroded by a solvent, so that it is difficult to remove dirt. On the other hand, the molded article obtained by the method of the present invention does not have such disadvantages and is excellent in appearance. Further, when used in a lighting part as an alternative to a glass plate, various properties such as anti-glare properties, light weight, impact resistance, and safety at breakage can be utilized. Still other applications include various shelves and dividers, building, building wallboards, waistboards, blindboards, and the like.

[0014]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. In the examples, "parts" means parts by weight. The physical properties were measured as follows. Intrinsic viscosity; 1.00 g of polyester mixed solvent 10 of phenol / tetrachloroethane = 50/50 (weight ratio)
It was dissolved in 0 ml and measured at 30 ° C. Light transmittance: Total light transmittance was measured according to JIS K-7105. Gloss: Measured according to JIS K-7105, with both the incident angle and the light receiving angle being 60 degrees.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.84 dl / g was dried under vacuum at 160 ° C. for 4 hours, and then dried at 290 ° C.
And extruded into a sheet shape, and brought into contact with a casting roll to prepare a polyester sheet having a thickness of about 5 mm. A test piece of 500 × 500 mm was cut out from the obtained polyester sheet, and a test piece of 40 × 500 mm was obtained by plug-assist method.
A 0 × 400 × 100 mm lighting fixture cover was made. At the time of molding, the sheet is heated to about 110 ° C. by measuring with a radiation thermometer, and then room temperature air containing about 100 g / m ³ of water is applied to the outer side of the cover to form a mat-like cover. The droplets were sprayed at about 50 to 100 g / m ^2, and the plug was activated immediately. The gloss of the obtained molded product was 25%, and the light transmittance was 80%. When water is sprayed on both sides of the heated sheet, a cover having a matte tone on both sides is obtained.

Example 2 500 × 5 from the polyester sheet obtained in Example 1.
00 specimen was cut out and used for 100 × 100 ×
A 50 mm outer surface mat-like container was manufactured by a plug assist method. In molding, about 50 to 100 g / m ² and room temperature air containing about 100 g / m ³ of water on the side to be the outer surface of the container of the heated sheet to about 110 ° C. as droplets
Immediately after being sprayed so as to be molded. The gloss of the obtained molded product was 25%, and the light transmittance was 85%.

Example 3 Polyethylene terephthalate having an intrinsic viscosity of 0.75 dl / g was dried under vacuum at 160 ° C. for 4 hours, and then dried at 290 ° C.
And extruded into a sheet shape, and brought into contact with a casting roll to prepare a polyester sheet having a thickness of about 1 mm. 2,000 x 2,000 m from the obtained polyester sheet
m was cut out and a box-shaped container of 1,900 × 1,900 × 200 mm was manufactured using the same by the plug assist method. In molding was blowing air at room temperature which contained about 100 g / m ³ of water on the side to be the outer surface of the container of the heated sheet to about 110 ° C. to approximately 50 to 100 g / m ² as droplets After that, it was molded immediately. A flat plate cut out from the bottom of the obtained molded product had a gloss of 42% and a light transmittance of 78%, and was suitable for a skylight for lighting, a shelf of a display shelf, a partition plate and the like.

Example 4 The procedure of Example 3 was repeated, except that the moisture content of the air blown on the heated polyester sheet was 50 g / m ³ , and the spray amount was about 50 g / m ² as droplets. Vacuum forming was performed in exactly the same manner as in Example 3. The resulting molded article had a glossiness of 42% and a light transmittance of 70%, and had a finer matte tone than that of Example 3.

Claims (9)

[Claims] 1. A method for thermoforming a polyester sheet, wherein fine droplets are sprayed on the polyester sheet to generate a finely distributed temperature non-uniform state on the surface of the polyester sheet. A method for producing a polyester molded article having a glossiness of one surface of 90% or less. 2. The method for producing a polyester molded article according to claim 1, wherein droplets are sprayed onto the polyester sheet while its surface temperature is 80 ° C. or higher. 3. When the polyester sheet is thermoformed, while the polyester melt-extruded into a sheet shape as a polyester sheet is at a high temperature, fine droplets are sprayed onto the polyester sheet and the temperature of the polyester finely distributed on the surface is reduced. A method for producing a polyester molded article having a glossiness of at least one surface of 90% or less, characterized by using a polyester sheet produced through a process for producing a non-uniform state. 4. When the polyester sheet is thermoformed, while the polyester melt-extruded into a sheet shape as a polyester sheet is at a high temperature, fine droplets are sprayed onto the polyester sheet so that the temperature of the polyester is finely distributed on the surface. Using a polyester sheet manufactured through a process of generating a non-uniform state, and spraying fine droplets onto the surface of the polyester sheet during the thermoforming while the surface temperature of the polyester sheet is 80 ° C. or higher, A method for producing a polyester molded article having a glossiness of at least one surface of 90% or less, characterized by causing a temperature non-uniform state which is finely distributed. 5. The polyester molded article according to claim 4, wherein the average diameter of the droplets sprayed on the polyester melt-extruded into a sheet is different from the average diameter of the droplets sprayed during thermoforming. Production method. 6. The method for producing a polyester molded article according to claim 1, wherein the spraying is performed so as to include droplets of 10 to 500 g / m ³ . 7. The method for producing a polyester molded article according to claim 1, wherein the glossiness of at least one surface is 50% or less. 8. The method for producing a polyester molded article according to claim 1, wherein the light transmittance of the molded article is 60 to 90%. 9. The method for producing a polyester molded product according to claim 1, wherein the polyester molded product is a light-transmitting cover of a lighting fixture.