JP4801188B2 - Method for producing ethylene-vinyl acetate copolymer resin sheet - Google Patents

Description

  The present invention relates to a method for producing a sheet of an ethylene-vinyl acetate copolymer resin (hereinafter sometimes referred to as EVA resin) containing an organic peroxide using an extruder.

EVA resin sheets cross-linked with an organic peroxide are excellent in transparency, weather resistance, chemical resistance, and adhesiveness, and are therefore used as safety glass interlayers and electronic component sealing materials. In particular, in recent years, the demand is increasing as a sealing material for solar cell modules.
The EVA resin sheet usually has a melting point of about 70 ° C to 90 ° C. In order to improve the heat resistance, a method of crosslinking an EVA resin using an organic peroxide is known (see Patent Documents 1 to 4). Examples of such organic peroxides include dialkyl peroxides, alkyl peroxyesters, and peroxyketals. These substances are usually liquid at room temperature, unstable to heat, and flammable. From the viewpoint of ensuring safety during handling, these organic peroxides are made into master batches. Increasing use of contained pellets is increasing. Various additives such as an antioxidant, an ultraviolet absorber, and a light stabilizer are blended for the purpose of preventing yellowing of the EVA resin sheet, improving weather resistance, improving light resistance, and the like.

As an EVA resin sheet manufacturing method, there is an extrusion molding method. In order to melt and plasticize an EVA resin in an extruder, it is necessary to raise the resin temperature to the melting point or higher. On the other hand, the decomposition temperature of the organic peroxide having a half-life of 10 hours is approximately 140 ° C. or less. Therefore, in order to produce an EVA resin sheet while suppressing the decomposition of the organic peroxide, the resin temperature during molding is limited to a relatively narrow range.
Single-screw extruders are suitable for applications that stably extrude resins at low temperatures, but the need for kneading with the various additives described above has increased, so the adoption of twin-screw extruders is increasing. Advanced technology is required to extrude at a low temperature while increasing the kneading degree using a twin-screw extruder, but organic peroxide-containing pellets, EVA pellets, and various additives are collectively fed into the most upstream part of the extruder. Thus, a technique for manufacturing an EVA resin sheet is being established.

JP 2008-138125 A JP 2008-159856 A JP-A-10-98206 JP 2001-240710 A

  Since the organic peroxide in the organic peroxide-containing pellet is heated in the manufacturing process of the pellet, there is a high possibility that the half-life is shortened. Therefore, the organic peroxide-containing pellets supplied into the cylinder from the raw material supply port in the most upstream part of the extruder are highly likely to start the crosslinking of the EVA resin in the middle to the downstream part of the extruder. In addition, when organic peroxide and EVA resin are mixed in advance and fed into the cylinder from the raw material supply port, a screw with strong kneadability is used in the region where the EVA resin is melt-plasticized, so the temperature of the EVA resin There is a possibility that it becomes locally high, and this is likely to initiate crosslinking of the EVA resin.

  As a result of the crosslinking of the EVA resin, there may be a problem that the long-term continuous molding operation of the EVA resin sheet cannot be performed and the productivity is lowered and the quality of the EVA resin sheet is lowered. The present invention aims to solve these problems.

  The present invention relates to a method for producing an ethylene-vinyl acetate copolymer resin-containing sheet containing an organic peroxide using an extrusion molding machine. First, the resin is cylinderized from a raw material supply port at the most upstream part of the extrusion molding machine. The organic peroxide is added into the cylinder between the raw material supply port and the screw tip using a liquid addition nozzle, and the resin and the organic peroxide are mixed in the extruder. Thereafter, a resin having a gel fraction of 0% is extruded from a die at the tip of the extruder.

  ADVANTAGE OF THE INVENTION According to this invention, an organic peroxide and EVA resin can be stably and quantitatively mixed homogeneously in an extrusion molding machine, and an EVA resin sheet having excellent quality can be molded continuously for a long period of time.

1 is a schematic view of a twin-screw extruder or the like for carrying out the method for producing an EVA resin sheet of the present invention. It is a figure which shows the screw shape used in the Example or the comparative example.

Examples of the extruder used for the production of the EVA resin sheet of the present invention include various known biaxial extruders and single screw extruders. A typical extrusion molding machine has a structure in which a hopper as a raw material supply port is installed at the most upstream part and a die such as a T die or a ring die is installed at the most downstream end part. A screw is arranged in the cylinder, and the resin raw material put in the cylinder is heated and melted by a heater arranged outside the cylinder, and is sent in the downstream direction by a rotating screw. Extruded.
As the extruder, it is preferable to use a twin screw extruder excellent in kneading performance in order to sufficiently mix the additive with the resin. However, since the twin screw extruder is not filled with resin in many areas in the cylinder, the extrusion stability (resin pressure stability before the T-die) is poor, and the gear pump is extruded to solve this problem. It is preferable to attach to the front end of the machine. The gear pump is disposed between the screw tip and the die.

  Examples of the ethylene-vinyl acetate copolymer resin used in the present invention include those having a vinyl acetate unit content of about 10 to 35% by mass and a melt flow rate of about 1 to 30 g / min.

  Examples of the organic peroxide used in the present invention include 2-ethylhexanoxycarbonyl-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis ( t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3,1,3-bis (2-t-butylperoxyisopropyl) benzene, di-t- Dialkyl peroxides such as butyl peroxide; t-butyl peroxyisobutyrate, t-butyl peroxymaleic acid, t-butyl peroxyisonanoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2 -Ethylhexyl carbonate, t-butyl peroxyacetate, t-butyl pero Alkyl peroxyesters such as cibenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, 2,5-dimethylhexyl-2,5-bisperoxybenzoate; 1,1-bis (t -Butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-amylperoxy) cyclohexane, 2,2-bis (t Peroxyketals such as -butylperoxy) butane, n-butyl-4,4-bis (t-butylperoxy) valerate, ethyl-3,3-bis (t-butylperoxy) butyrate, and the like.

Among these, t-butyl cumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, 1,3-bis (2-t-butylperoxyisopropyl) benzene, 2,2-bis (t-butylperoxy) butane has a half-life temperature of 140 ° C. or higher because the resin temperature in the cylinder, in the die and during die extrusion is 140 ° C. or lower. An EVA resin sheet having a gel fraction of 0% can be produced.
In addition, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, n-butyl-4,4-bis (t-butylperoxy) valerate and the like have a half-life temperature of 120 hours. Since the temperature is higher than or equal to ° C., an EVA resin sheet having a gel fraction of 0% can be manufactured by setting the resin temperature in the cylinder, in the die and during die extrusion to 120 ° C. or lower.

The amount of the organic peroxide used is preferably about 0.1 to 5.0 parts by mass and more preferably about 0.5 to 3.5 parts by mass with respect to 100 parts by mass of the EVA resin.
In the present invention, the organic peroxide is added into the cylinder between the raw material supply port and the screw tip using a liquid addition nozzle. A well-known thing can be used as a liquid addition nozzle.

  In the extruder, a kneading step using a kneading screw is necessary for melt plasticizing the EVA resin and mixing the organic peroxide. In the conventional process of supplying the organic peroxide and the EVA resin from the raw material supply port, the melt plasticization of the EVA resin and the mixing of the organic peroxide are simultaneously performed, and extremely high kneading energy is imparted to the EVA resin. . This energy leads to an increase in the resin temperature, and the temperature of the extruded EVA resin tends to increase. On the other hand, in the method of directly adding the organic peroxide into the cylinder, the addition and mixing of the organic peroxide can be performed after the melt plasticization of the EVA resin, so that the kneading energy can be reduced. As a result, this method can suppress the heat generation of the EVA resin.

  The EVA resin gel fraction (%) is obtained by immersing 1 g of EVA resin sheet in 100 ml of xylene, heating at 110 ° C. for 24 hours, filtering through a wire mesh, collecting insoluble matter, drying, and weighing. Can be measured.

The uncrosslinked EVA resin sheet extruded from a T-die or the like is cooled and solidified with a uniform thickness by a cooling roll and wound up by a winder.
This uncrosslinked EVA resin sheet is subjected to a crosslinking treatment and used as a crosslinked EVA resin sheet. The crosslinked EVA resin sheet can be used as an adhesive, a sealing material for electronic materials, a sealing film for solar cells, and the like.

  When manufacturing an organic resin-containing EVA resin sheet, when adding an antioxidant, an ultraviolet absorber, a light stabilizer, etc., these additives are generally in a solid state at room temperature. It is possible to adopt a batch feeding method that feeds and feeds to the raw material supply port with individual feeders.

[Example 1]
The screw of the structure of FIGS. 2-1 was attached to the biaxial extruder of FIG. 1, and the EVA resin sheet was manufactured in the following procedures.
The EVA resin was supplied using a gravimetric feeder, and the antioxidant was supplied to the raw material supply port of the biaxial extruder using a powder quantitative feed feeder. An organic peroxide was supplied to the liquid addition nozzle installed at the intermediate part between the raw material supply port and the screw tip using a plunger pump, and the organic peroxide was injected into the cylinder from the liquid addition nozzle. The blending ratio of the raw materials was 100 parts by mass of EVA resin (MFR = 15 g / 10 min, melting point 75 ° C.), 1.0 part by mass of organic peroxide (2-ethylhexanoxycarbonyl-tert-butyl peroxide), and oxidation. The amount of the inhibitor (Irganox 1010) was 0.2 parts by mass. The temperature of this organic peroxide having a half-life of 1 hour was 119 ° C., and the temperature of a half-life of 10 hours was 99 ° C. The EVA resin supply rate was 150 kg / H, and a 0.5 mm thick resin sheet was obtained. The resin temperature at the T-die outlet was 103 ° C.
The gel fraction of the resin extruded from the T-die outlet was measured every 30 minutes from the start of operation. The gel fraction up to 6 hours was 0%, which was substantially uncrosslinked.

[Comparative Example 1]
The same EVA resin and organic peroxide as those used in Example 1 were mixed in advance at a ratio of 100: 1 (parts by mass) and supplied to the raw material supply port of the biaxial extruder, from the liquid addition nozzle. Did not supply organic peroxide. Moreover, the screw of the structure of FIGS. 2-2 was used and the other conditions were carried out similarly to Example 1, and obtained the resin sheet. The resin temperature at the T-die outlet was 112 ° C.
The gel fraction after 30 minutes from the start of operation was 0% and was substantially uncrosslinked, but the gel fraction after 60 minutes increased to 11.5%.

[Comparative Example 2]
In order to set the resin temperature at the T-die outlet to the same level as in Example 1, the screw of FIG. 2-3 having a shorter kneading part than Comparative Example 1 was used, and other conditions were the same as in Comparative Example 1. Thus, a resin sheet was obtained. The resin temperature at the T-die outlet was 102 ° C.
From 6 hours after the start of operation, the gel fraction was 0%, which was substantially uncrosslinked. However, unmelted EVA resin was observed in the resin extruded from the T-die immediately after the start of operation until 6 hours later.

Example 1 and Comparative Example 1 (prior art embodiment) are carried out under the same operating conditions except that the addition position of the organic peroxide and the screw shape are different. The resin temperature at the die outlet was 10 ° C. higher than that in Example 1, and a crosslinked product was generated after 60 minutes from the start of operation. On the other hand, in Comparative Example 2, a screw-shaped screw was used in which the kneading energy was weakened so that the resin temperature at the T-die outlet was almost the same as in Example 1. Unmelted resin was observed inside.
From the above comparison, it can be seen that the molding method of the present invention enables sufficient melt plasticization of the EVA resin, kneading of the organic peroxide, and continuous operation with the resin temperature suppressed.

DESCRIPTION OF SYMBOLS 1 Twin screw extruder 2 Motor 3 T die 4 Gear pump 5 Screen 6 Feeder 7 Plunger pump 8 Liquid addition nozzle 9 Cooling port 10 Winding machine 11 Raw material supply port 12 Cylinder 13 Transport part 14 Kneading part

Claims (5)

  In a method of producing an ethylene-vinyl acetate copolymer resin-containing sheet containing an organic peroxide using an extruder, first, the resin is introduced into a cylinder from the raw material supply port at the most upstream part of the extruder. Then, an organic peroxide is added into the cylinder between the raw material supply port and the screw tip using a liquid addition nozzle, and the resin and the organic peroxide are mixed in the extruder, and then extruded. A method for producing a sheet-like product, wherein a resin having a gel fraction of 0% is extruded from a die at the tip of a molding machine.   The method according to claim 1, wherein an extruder having a twin screw extruder and a gear pump is used.   The method according to claim 1, wherein the organic peroxide is added in an amount of 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the resin.   The organic peroxide having a half-life of 1 hour as an organic peroxide having a temperature of 140 ° C or lower is used, and the resin temperature at the time of die extrusion is 140 ° C or lower. The method described.   The organic peroxide having a half life of 1 hour as an organic peroxide having a temperature of 120 ° C or lower is used, and the resin temperature during die extrusion is 120 ° C or lower. The method described.

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