JP2005314685A - Method for producing low outgassing resin, and vinyl chloride resin, polyethylene resin and hydrogenated styrenic thermoplastic elastomer produced by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a low outgassing resin, by which the resin can be treated with a simple apparatus at a low temperature to easily reduce the outgassing amount of the resin to a low concentration, and to provide vinyl chloride resin, polyethylene resin and a hydrogenated styrenic thermoplastic elastomer which are produced by the method and whose outgassing amounts are little. <P>SOLUTION: This method for producing the low outgassing resin is characterized by charging the resin into a drier having a stirring function and then heating the resin, while blowing in a gas. And the vinyl chloride resin is characterized by being produced by the method and having an outgassing amount of ≤5 wt. ppm. The polyethylene resin is characterized by being produced by the method and having an outgassing amount of ≤25 wt. ppm. The hydrogenated styrenic thermoplastic elastomer is characterized by being produced by the method and having an outgassing amount of ≤5 wt. ppm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a low outgas resin, and a vinyl chloride resin, a polyethylene resin and a hydrogenated styrene-based thermoplastic elastomer produced by the method. More specifically, the present invention relates to a method for producing a low outgas resin capable of easily reducing the outgas amount of the resin to a low concentration by processing at a low temperature using a simple apparatus, and the method. The present invention relates to a vinyl chloride resin, a polyethylene resin, and a hydrogenated styrene thermoplastic elastomer with a small amount of outgas.

Containers for storing semiconductor materials such as silicon wafers, electric wires and cables used in clean rooms are required to have extremely high cleanliness. Plastic containers are often used for the above containers, but in the case of containers that contain semiconductor materials, very small amounts of moisture, residual solvents, residual monomers, etc. contained in the molding materials are outgassing from the molded articles. Volatilizes and is adsorbed by semiconductor materials and contaminates materials. Residual solvents and residual monomers that contaminate the inside of the clean room are also not preferred in the vinyl chloride resin used for covering the wires and cables used in the clean room. For this reason, attempts have been made to develop a technique for removing residual solvent and residual monomer to an extremely low level from a resin having residual solvent and residual monomer of about several hundred ppm by weight.
For example, since the content of low molecular components is small, the low molecular component having a molecular weight of 140 to 400 is less than 1,000 ppm as a styrene resin composition having a very low elution or volatilization amount. A styrene-based resin composition having a content of less than 500 ppm was proposed, and after removing the volatile components by heat-treating the polystyrene obtained by anionic polymerization in a flashing tank with reduced pressure, the remaining volatile components were removed with a vented extruder. An example of removal is shown (Patent Document 1). However, the amount of residual solvent in the mixed resin of polystyrene and styrene block copolymer produced in this way is about 50 ppm, and a sufficient residual solvent removing effect is not obtained.
As a water injection foaming devolatilization method that can efficiently remove volatile components from the polymer melt, a decompression expansion zone is provided between the water injection dispersion zone and the devolatilization zone of the extruder, and the water dispersed in the polymer melt A water injection foaming devolatilization method has been proposed in which bubbles are allowed to grow and bubbles are collapsed at the downstream end of the reduced pressure expansion zone (Patent Document 2). In addition, as a degassing method for the molten resin, the temperature of the molten resin at the interface between the bubble of water added to the molten resin and the molten resin and the temperature of the molten resin in the vicinity thereof can be improved, and the degassing efficiency is improved. Proposed a method to stir molten resin containing water bubbles downstream of the dispersion foaming zone to stir the molten resin, and then degas the volatiles in the resin in the downstream degassing zone (Patent Document 3). However, when water is added to the molten resin, volatile components are removed by azeotropy with water, but moisture may remain in the product. In addition, the twin-screw extruder is not only expensive in capital investment, but also inevitably becomes a high-temperature treatment in order to melt the resin, and has a problem in terms of resin quality deterioration.
Furthermore, as a polyvinyl chloride resin composition coated electric wire / cable suitable for use in a clean room that suppresses the generation of airborne contaminants, it contains calcium soap, zinc soap, or hydrotalcite, lead compounds, and a melting point of 100 There has been proposed an electric wire / cable coated with a polyvinyl chloride resin composition that does not contain any β-diketone compound at a temperature not higher than ° C. (Patent Document 4). However, it has been difficult to reduce the amount of outgas to less than 400 ppm only by selecting the compound for the vinyl chloride resin.
JP 2002-53719 A (pages 2, 5, 14) Japanese Patent Laid-Open No. 7-164509 (2nd page) JP 2002-326273 A (second and third pages) JP 2002-352629 A (2nd page)

  The present invention relates to a method for producing a low outgas resin capable of easily reducing the outgas amount of the resin to a low concentration by processing at a low temperature using a simple apparatus, and an outgas produced by the method. The object of the present invention is to provide a small amount of vinyl chloride resin, polyethylene resin and hydrogenated styrene thermoplastic elastomer.

As a result of intensive studies to solve the above-mentioned problems, the present inventor charged the resin into a dryer having a stirring function, and heated while blowing the gas, so that the amount of outgas in the resin was easily 25 ppm by weight. The inventors have found that it can be reduced below, and have completed the present invention based on this finding.
That is, the present invention
(1) A method for producing a low-outgas resin, comprising charging a resin into a dryer having a stirring function, and heating while blowing gas;
(2) The method for producing a low outgas resin as described above, wherein the inside of the dryer is depressurized to 101 to 1 kPa,
(3) The method for producing a low outgas resin as described above, wherein the amount of gas blown is 1 to 16 L (standard state) / min per 1 kg of resin;
(4) A method for producing a low-outgas resin as described above, wherein gas is blown into a resin layer in a dryer.
(5) The method for producing a low outgas resin according to the above, wherein the dryer having a stirring function is a conical dryer,
(6) The method for producing a low-outgas resin as described above, wherein the gas is nitrogen,
(7) The method for producing a low outgas resin as described above, wherein the amount of residual organic matter in the resin is 1,000 ppm by weight or less,
(8) A vinyl chloride resin produced by the method described above, wherein the amount of outgas is 5 ppm by weight or less,
(9) A polyethylene resin produced by the method described above, wherein the outgas amount is 25 ppm by weight or less, and
(10) A hydrogenated styrene-based thermoplastic elastomer produced by the method described above, wherein the outgas amount is 5 ppm by weight or less,
Is to provide.

  According to the method for producing a low outgas resin of the present invention, a simple operation of charging a resin into a dryer having a stirring function and heating while blowing the gas, there is no fear of thermal degradation due to melting of the resin, and the resin is originally The outgas amount can be reduced while maintaining the good physical properties. The low outgas resin produced by the method of the present invention is useful as a raw material for plastic products used in a clean room, a coating material for electric wires and cables used in a clean room, and a raw material for food containers. The polyvinyl chloride resin and hydrogenated styrene thermoplastic elastomer having an outgas amount of 5 ppm by weight or less and the polyethylene resin having an outgas amount of 25 ppm by weight or less produced by the method of the present invention are particularly useful as these raw materials.

In the method for producing a low outgas resin of the present invention, the resin is charged into a dryer having a stirring function and heated while blowing gas.
In the present invention, the low outgas resin means a resin having an outgas amount of 25 ppm by weight or less. The amount of outgas is preferably 10 ppm by weight or less, particularly preferably 5 ppm by weight or less.
In the present invention, “resin” means “resin pellet”, “resin powder” and “crushed resin”. Among these, “resin pellet” or “resin powder” is preferable, and “resin pellet” is particularly preferable.
The amount of outgas is as follows: (a) Small pieces or small particles of 0.02 g or less of resin, and (b) A sample container made of a glass tube with an inner diameter of 4 mm from which moisture and organic substances adsorbed on the surface are completely removed. C) The container is heated while flowing helium at 30 mL / min, and the gas flowing out from the container is collected while maintaining the temperature at 100 ° C. for 60 minutes. (D) The collected gas is subjected to thermal desorption chromatography. The value obtained by analysis using an analyzer.
Examples of the dryer having a stirring function used in the method of the present invention include a grooved stirring dryer, a cylindrical stirring dryer, a conical ribbon stirring dryer, a conical screw stirring dryer, and a conical (conical rotation) stirring dryer. , Rotary dryers with steam tubes, outer wall heating rotary dryers, conduction heat dryers such as vibratory fluid dryers, fluidized bed dryers, rotary dryers, rapid dryers, aeration rotary dryers, and multistage disk dryers And convection heat transfer dryers.
The dryer having a stirring function used in the method of the present invention is a device having a resin and a gas phase in the apparatus and stirring the resin, and preferably a dryer in which the resin forms a resin layer during the devolatilization operation. Can be used. Examples of such a dryer include a conical dryer and a dryer in which a container containing a resin such as a rotary kiln rotates and stirs; a horizontal type or vertical type such as a paddle dryer, a disc dryer, a torus disc, and solid air. And a dryer that rotates a stirring blade installed in a mold container to stir the resin. Among these, a dryer in which the container itself containing the resin rotates and agitates can be preferably used, and a conical dryer can be particularly preferably used. Since the conical dryer does not have a stirring blade, there is no adhesion of the resin to the stirring blade or aggregation of the resin due to the shearing force of the stirring blade, high devolatilization efficiency, low frequency of cleaning work, low quality and low quality. Outgas resin can be obtained.
In the method of the present invention, when a dryer in which a container containing resin is rotated and stirred is used as a dryer having a stirring function, the number of rotations is preferably 6 to 30 rpm, and preferably 9 to 20 rpm. More preferred. If the rotational speed is less than 6 rpm, the effect of reducing the outgas amount may not be sufficiently exhibited. When the rotation speed exceeds 30 rpm, noise generated from the dryer increases, which may increase the power cost.

The low outgas resin produced by the method of the present invention is not particularly limited. For example, polyvinyl chloride resin, acrylonitrile-butadiene-styrene copolymer resin (ABS), methacrylic resin, polyamide resin, polycarbonate resin, polyester resin, polyethylene resin, A polypropylene resin, a resin having an alicyclic structure, a polystyrene resin, a polysulfone resin, a hydrogenated styrene thermoplastic elastomer (SEBS), a fluororesin, and the like can be given. Among these, the method of the present invention is particularly suitable for polyvinyl chloride resins, polyethylene resins, and hydrogenated styrene-based thermoplastic elastomers whose reduction in outgas amount is not easy despite the high demand for materials for clean rooms. Can be applied.
In the method of the present invention, the heating temperature of the resin is preferably 40 to 300 ° C, more preferably 70 to 140 ° C, and particularly preferably 90 to 120 ° C. If the heating temperature is less than the above range, the outgas amount may not be sufficiently reduced. If the heating temperature exceeds the above range, the resins may be fused together to cause lumps. The heating temperature is preferably 5 to 10 ° C. lower than the melting point of the resin to which the method of the present invention is applied. In the method of the present invention, the method of heating the resin is not particularly limited. For example, the resin can be heated by providing a jacket in a container charged with the resin and passing through a heating medium, steam or the like.

In the method of the present invention, it is preferable to reduce the pressure in the container of the dryer for charging the resin. By reducing the pressure in the container in which the resin is charged, the effect of removing the outgas component from the resin can be enhanced. The pressure inside the container of the dryer is preferably 101 to 1 kPa, more preferably 20 to 5 kPa as an absolute pressure. In order to make the pressure less than the above range, a high-capacity vacuum pump is necessary to maintain a low pressure while blowing gas, which may increase initial investment and operating costs.
Examples of the gas used in the method of the present invention include inert gases such as nitrogen, helium, and argon, and air. Among these, nitrogen has an effect of preventing deterioration of the resin to be heated, and can be suitably used because it is relatively inexpensive among inert gases.
In the method of the present invention, the amount of gas blown is preferably 1 to 16 L (standard state) / min per kg of resin, and more preferably 2 to 8 L (standard state) / min. If the amount of gas blown is less than 1 L (standard state) / min per kg of resin, the outgas amount may not be sufficiently reduced. If the amount of gas blown exceeds 16 L (standard state) / min per kg of resin, the processing cost may be excessive, or the resin may be entrained in the gas flow.
The amount of residual organic matter in the raw material resin that reduces the outgas amount by applying the method of the present invention is preferably 1,000 ppm by weight or less, more preferably 500 ppm by weight or less, and 300 ppm by weight or less. Is more preferable. If the amount of residual organic matter in the raw material resin exceeds the above range, it may be difficult to produce a low outgas resin with a sufficiently reduced outgas amount. The amount of residual organic matter is a value determined by the same method as the amount of outgas.

In the method of the present invention, the means for blowing gas into the resin charged in the dryer is not particularly limited. For example, a gas blowing nozzle can be provided in a container charged with resin. A double pipe structure in which a gas blowing pipe is installed in the suction pipe connected to the vacuum line can be suitably used.
In the method of the present invention, there is no particular limitation on the position where the gas is blown in the container charged with the resin (in the dryer). For example, the gas can be blown into the resin layer, or the gas is blown into the gas phase. You can also. Of these gas blowing positions, gas is preferably blown into the resin layer. By blowing gas into the resin layer, the devolatilization efficiency can be increased and a resin with a small outgas amount can be efficiently produced. The gas blowing into the resin layer can be carried out continuously or intermittently. For example, when a conical dryer is used, the resin layer moves as the container rotates, and the state where the gas is blown into the resin layer and the state where the gas is blown into the gas phase may appear alternately. Efficient devolatilization can be performed if the state of blowing gas into the layer can be ensured intermittently.
FIG. 1 is a system diagram of one embodiment of an apparatus used in the method for producing a low outgas resin of the present invention. Resin as a raw material is charged into the conical container 8. The conical container is heated by introducing steam from the steam introducing unit 3 into the jacket. The drain generated by the condensation of steam is discharged from the drain discharge pipe 4. Nitrogen is sent from the nitrogen introduction part 1 to the conical container, and nitrogen is blown from the blowing nozzle 5 provided in the gas phase or the blowing nozzle 6 provided in the resin layer. The gas in the conical container is sucked from the suction port 7 and discharged out of the system via the vacuum line 2. After devolatilization by heating while blowing gas for a predetermined time, cold water is sent to the jacket of the conical container to cool it, and the low outgas resin is taken out from the conical container.

The vinyl chloride resin of the present invention is a vinyl chloride resin having an outgas amount of 5 ppm by weight or less produced by the method of the present invention. The polyethylene resin of the present invention is a polyethylene resin having an outgas amount of 25 ppm by weight or less produced by the method of the present invention. The hydrogenated styrene thermoplastic elastomer (SEBS) of the present invention is a hydrogenated styrene thermoplastic elastomer produced by the method of the present invention and having an outgas amount of 5 ppm by weight or less. For plastic molded products, plastic-coated wires and cables manufactured by injection molding, extrusion molding, compression molding, extrusion coating processing, etc., using resin whose outgas amount is below the above range, depolymerization of the resin during molding processing Even if the outgas amount increases due to side reactions such as the above, it can still be safely used because it is below the level of outgas amount required for equipment in a clean room or as a food packaging container.
Resin with the outgas amount produced by the method of the present invention below the above range is received when starting from the same raw resin as compared to the low outgas resin produced by the water injection devolatilization method using a twin screw extruder. Since the heat history is remarkably small, there is little decrease in the degree of polymerization and generation of by-products due to thermal deterioration, and good physical properties are maintained. In addition, the low outgas resin produced by the water injection devolatilization method cannot avoid the residual moisture even though it is small, whereas the low outgas resin produced by the method of the present invention does not contain any moisture. A molded product having a good appearance can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In Examples and Comparative Examples, evaluation was performed by the following method.
(1) Outgas amount 0.05 g of cylindrical resin pellets having a diameter of about 4 mm and a length of about 4 mm were precisely weighed, cut into four on two orthogonal planes including the central axis of the cylinder, and adsorbed on the surface The sample container is made of a glass tube having an inner diameter of 4 mm from which moisture and organic substances have been completely removed. Next, while flowing helium as an inert gas in the container at a flow rate of 30 mL / min, the container is heated at a temperature of 100 ° C. for 60 minutes to continuously collect gas flowing out from the container. Next, the collected gas is analyzed using a thermal desorption gas chromatography mass spectrometer [manufactured by Yokogawa Analytical Systems Co., Ltd.], the amount of organic matter released is measured, and the unit of weight ppm (μg organic matter / g resin) It shows with. The resin powder is analyzed as it is without being cut.
(2) Moisture content A cylindrical resin pellet having a diameter of about 4 mm and a length of about 4 mm is precisely weighed, cut into a thickness of about 1 mm on a plane perpendicular to the central axis of the cylinder, and a stage temperature of 120 ° C. in a vacuum. For 30 minutes, and then analyzed using a temperature-programmed desorption gas analyzer [Rigaku Corp., TPD type R] to measure the amount of water released and expressed in units of ppm by weight (μg moisture / g resin). The resin powder is analyzed as it is without being cut.
Further, as a dryer having a drying function, a conical dryer (manufactured by Kashiwagi Machinery Co., Ltd., vacuum tumble dryer, internal volume 250 L) incorporated in the system shown in FIG. 1 was used. The resin is flowed by rotating the conical container 8 around the center of the conical main body, and the pressure is reduced by a vacuum pump connected to the vacuum line 2, and the conical main body jacket is heated through hot water or steam, and the residual solvent in the resin Residual monomer and moisture were removed. The gas blowing line has a double pipe structure with a suction pipe, and even if the conical container 8 is rotated, the suction port 7 and the tip position 5 or 6 of the gas blowing nozzle do not change. When gas was blown into the resin layer, the tip of the blow nozzle was provided at position 6, and when the gas was blown into the gas phase, the tip of the blow nozzle was provided at position 5.

Example 1
A low outgas resin was produced using hydrogenated styrene thermoplastic elastomer [Asahi Kasei Co., Ltd., Tuftec H1062] pellets as resin pellets. This hydrogenated styrene-based thermoplastic elastomer pellet had a columnar shape with a diameter of about 4 mm and a length of about 4 mm, an outgas amount of 176 ppm by weight, a moisture content of 35 ppm by weight, and a decomposition start temperature of 245 ° C.
The tip of the gas blowing nozzle of the conical dryer was provided in the layer of resin pellets (position 6 in FIG. 1), and 50 kg of resin pellets were charged into the conical container. Industrial nitrogen was blown at a flow rate of 120 L (standard state) / min, the conical container was rotated at 12 rpm, the inside of the conical container was depressurized, and steam was passed through the jacket. The pressure control valve at the jacket inlet and the outlet valve opening were adjusted, and the jacket pressure was controlled to 0.20 MPa as an absolute pressure. About 30 minutes were required until steady operation, and the jacket temperature at this time was 120 ° C. and the resin pellet temperature was 112 ° C. The absolute pressure in the conical container was 5.3 kPa. After maintaining this state for 6 hours, cooling water was passed through the jacket for about 30 minutes to cool the resin pellets to 30 ° C. or less, and the resin pellets were analyzed. None of cyclohexane, ethylcyclohexane, ethylbenzene, styrene, and hexylbenzene was detected, and 3.2 ppm by weight of a high boiling point substance such as styrene dimer was detected as an outgas amount. Moisture was not detected.

Example 2
The same operation as in Example 1 was performed except that the gas blowing nozzle tip was provided in the gas phase (5 position in FIG. 1). The amount of outgas was 4.9 ppm by weight, and no water was detected.
Example 3
The same operation as in Example 1 was performed except that the jacket temperature was 130 ° C. and the resin temperature was 122 ° C. The amount of outgas was 2.3 ppm by weight, and no water was detected.
Example 4
The same operation as in Example 1 was performed except that the nitrogen blowing amount was 60 L (standard state) / min. Cyclohexane 0.7 wt ppm, styrene 0.1 wt ppm, hexylbenzene 0.1 wt ppm, high boiling point 7.1 wt ppm such as styrene dimer were detected, and the outgas amount was 8.0 wt ppm. Moisture was not detected.
Example 5
The same operation as in Example 1 was performed except that the nitrogen blowing amount was 240 L (standard state) / min. The amount of outgas was 2.3 ppm by weight, and no water was detected. Since nitrogen was blown in excess of the capacity of the vacuum pump, the pressure in the conical container rose to 10.6 kPa in absolute pressure.
Example 6
The same operation as in Example 1 was performed except that the nitrogen blowing amount was 480 L (standard state) / min. The amount of outgas was 2.8 ppm by weight, and no water was detected. Since nitrogen was blown in excess of the capacity of the vacuum pump, the pressure in the conical container rose to 19.8 kPa in absolute pressure.

Example 7
The same operation as in Example 1 was performed except that the absolute pressure in the conical container was 13.3 kPa. Cyclohexane 1.3 ppm by weight, styrene dimer and other high-boiling compounds 6.0 ppm by weight were detected, and the outgas amount was 7.3 ppm by weight. Moisture was not detected.
Example 8
The same operation as in Example 1 was performed except that the nitrogen blowing amount was 30 L (standard state) / min. 2.9 ppm by weight of cyclohexane, 0.1 ppm by weight of ethylcyclohexane, 2.4 ppm by weight of hexylbenzene, 14.0 ppm by weight of high-boiling substances such as styrene dimer were detected, and the amount of outgas was 19.4 ppm by weight. . Moisture was not detected.
Example 9
A low outgas resin was produced in the same manner as in Example 1 except that a hydrogenated styrene thermoplastic elastomer [Asahi Kasei Corporation, Tuftec H1051] pellet was used as the resin pellet. This hydrogenated styrene-based thermoplastic elastomer pellet had a columnar shape with a diameter of about 4 mm and a length of about 4 mm, an outgas amount of 106 ppm by weight, a moisture content of 40 ppm by weight, and a decomposition start temperature of 245 ° C. The outgas amount was 3.5 ppm by weight, and no water was detected.
Example 10
As the resin powder, a hydrogenated styrene thermoplastic elastomer [Asahi Kasei Co., Ltd., Tuftec H1051G] powder was used, and a low outgas resin was produced in the same manner as in Example 1. This hydrogenated styrene thermoplastic elastomer powder had a particle size of about 0.5 mm, an outgas amount of 41 ppm by weight, a moisture content of 35 ppm by weight, and a decomposition start temperature of 245 ° C. The amount of outgas was 2.0 ppm by weight, and moisture was not detected.

Comparative Example 1
The same operation as in Example 1 was performed except that nitrogen was not blown. 27.6 wtppm of cyclohexane, 11.5 wtppm of ethylcyclohexane, 18.5 wtppm of ethylbenzene, 0.4 wtppm of styrene, 52.3 wtppm of hexylbenzene, 66.2 wtppm of high boiling point substances such as styrene dimer The amount of outgas detected was 176.5 ppm by weight, and no residual organic matter could be removed. The moisture was 25 ppm by weight.
Comparative Example 2
Water injection zone on the barrel of a twin-screw fully meshing extruder [Toshiba Machine Co., Ltd., TEM-50B] with a screw diameter of 56 mm and a screw length of 2,340 mm and rotating in the same direction to the front of the outlet. And two devolatilization zones were provided.
The barrel temperature was set to 220 ° C., the same resin pellets as in Example 1 were supplied at 50 kg / h, the rotation speed was 200 rpm, and 8.3 mL / min of water was supplied from each water injection zone. The absolute pressure of was maintained at 5.3 kPa and devolatilized. As a result, it was discharged at a resin temperature of 245 ° C. Styrene 0.3 ppm by weight, hexylbenzene 5.2 ppm by weight, high boiling point substances 7.7 ppm by weight such as styrene dimer were detected, and the outgas amount was 13.2 ppm by weight. The water content was 75 ppm by weight.
The results of Examples 1 to 10 and Comparative Examples 1 and 2 are shown in Table 1.

As can be seen in Table 1, in Examples 1 to 10 in which hydrogenated styrene thermoplastic elastomer pellets or powders were charged into a conical dryer and heated while blowing nitrogen, the outgas amount of most product resins was 5 Weight ppm or less.
Comparing Example 1 in which nitrogen was blown into the resin pellet layer and Example 2 in which nitrogen was blown into the gas phase, it was found that blowing out nitrogen into the resin layer had a greater effect of reducing the outgas amount. In Example 3 in which the jacket temperature was increased, the amount of outgas decreased from that in Example 1. However, if the jacket temperature is too high, resin pellets may be fused. When Example 1, Examples 4 to 6, and Example 8 having different nitrogen blowing amounts are compared, it can be seen that the larger the nitrogen blowing amount, the greater the effect of reducing the outgas amount. However, if nitrogen is blown in excess of the capacity of the vacuum pump, the pressure of the container is not sufficiently reduced, and the effect of reducing the outgas amount is reduced. In Comparative Example 1 in which nitrogen was not blown in, the outgas amount of the product resin was not changed from the outgas amount of the raw resin, and it was found that there was no effect of reducing the outgas amount by simply heating under reduced pressure. In Comparative Example 2 in which water injection and devolatilization was performed using a twin screw extruder, the effect of reducing the outgas amount was not large, and the moisture content of the product resin increased from the moisture content of the raw resin.

Example 11
A low outgas resin was produced using a hard vinyl chloride resin compound pellet as the resin pellet. This hard vinyl chloride resin compound pellet has a cylindrical shape with a diameter of about 2.5 mm and a length of about 2.5 mm. As an outgas component, 2-ethylhexylaldehyde is 1.7 wtppm, 2-ethylhexanol is 3.1 wtppm. Acetophenone 1.3 wt ppm, α-methylstyrene 1.6 wt ppm, retention time 16.6 min peak component 0.9 wt ppm, retention time 16.8 to 16.9 min peak component 1.1 wt. The total outgas amount was 15.4 ppm by weight, including ppm, octyl benzoate 1.9 ppm by weight, bisphenol A 0.3 ppm by weight, and other 3.5 ppm by weight.
The tip of the gas blowing nozzle of the conical dryer was provided in the layer of resin pellets (position 6 in FIG. 1), and 25 kg of resin pellets were charged into the conical container. Industrial nitrogen at a temperature of 20 ° C. was blown at a flow rate of 120 L (standard state) / min, the conical container was rotated at 12 rpm, the inside of the conical container was reduced to 8.0 kPa in absolute pressure, and the jacket was heated to 125 ° C. After maintaining this state for 24 hours, cooling water was passed through the jacket for about 30 minutes to cool the resin pellets to 30 ° C. or less, and the resin pellets were analyzed. 2-ethylhexanol 0.1 wt ppm, octyl benzoate 0.1 wt ppm, bisphenol A 0.3 wt ppm and other 0.6 wt ppm were detected, and the outgas amount was 1.1 wt ppm. Moisture was not detected.
Example 12
The same operation as in Example 11 was performed except that the jacket temperature was set to 135 ° C. 2-ethylhexanol 0.1 ppm by weight, bisphenol A 0.4 ppm by weight, and other 0.6 ppm by weight were detected, and the outgas amount was 1.1 ppm by weight. Moisture was not detected.
Example 13
The same operation as in Example 11 was performed except that the conical container was rotated at 3 rpm and the jacket temperature was 90 ° C. Retention time of 16.8 to 16.9 minutes peak component 0.1 wtppm, octyl benzoate 0.2 wtppm, bisphenol A 0.2 wtppm, and other 0.8 wtppm were detected, and the outgas amount was 1. It was 3 ppm by weight. Moisture was not detected.
Example 14
Instead of nitrogen, air heated to 50 ° C. was blown at a flow rate of 120 L (standard state) / min, the conical vessel was rotated at 3 rpm, the inside of the conical vessel was reduced to 12.0 kPa in absolute pressure, and the jacket was brought to 90 ° C. The same operation as in Example 11 was performed except for heating. Octyl benzoate, 0.2 ppm by weight, 0.3 ppm by weight of bisphenol A, 0.9 ppm by weight of other components were detected, and the amount of outgas was 1.4 ppm by weight. Moisture was not detected.
The results of Examples 11-14 are shown in Table 2.

As can be seen in Table 2, in Examples 11 to 14, in which hard vinyl chloride resin compound pellets were charged into a conical dryer and heated under reduced pressure while blowing nitrogen or air, the outgas amount of the product resin was 1.4. Weight ppm or less.
Example 15
A low-outgas resin was produced using a high-density polyethylene resin [manufactured by Mitsui Chemicals, Inc.] pellet as the resin pellet. This high-density polyethylene resin pellet has a cylindrical shape with a diameter of about 3 mm and a length of about 3 mm, and as an outgas component, a hydrocarbon having 10 carbon atoms (C ₁₀ ), 85.3 ppm by weight, and a hydrocarbon having 12 carbon atoms (C ₁₂ ) 106.0 ppm by weight, hydrocarbon having 14 carbon atoms (C ₁₄ ) 118.0 ppm by weight, 2,6-di-t-butyl-4-methylphenol (BHT) 498.0 ppm by weight, 16 carbon atoms Hydrocarbon (C ₁₆ ) 120.0 ppm by weight, Carbon 18 hydrocarbon (C ₁₈ ) 108.0 ppm by weight, Carbon 20 hydrocarbon (C ₂₀ ) 64.5 ppm by weight, Carbon 22 Hydrogen (C ₂₂ ) 24.4 ppm by weight and other 102.8 ppm by weight were contained, and the total outgas amount was 1,227.0 ppm by weight.
The tip of the gas blowing nozzle of the conical dryer was provided in the layer of resin pellets (position 6 in FIG. 1), and 25 kg of resin pellets were charged into the conical container. Industrial nitrogen was blown at a flow rate of 120 L (standard state) / min, the conical container was rotated at 12 rpm, the inside of the conical container was reduced to 8.0 kPa, the jacket pressure was controlled to 0.30 MPa, and the jacket temperature was 133 ° C. did. After maintaining this state for 24 hours, cooling water was passed through the jacket for about 30 minutes to cool the resin pellets to 30 ° C. or less, and the resin pellets were analyzed. C ₁₈ 3.0 wt ppm, C ₂₀ 9.5 wt ppm, C ₂₂ 5.8 wt ppm, is detected other 4.4 wt ppm, outgas amount was 22.7 wt ppm. Moisture was not detected.
In Example 15 in which high-density polyethylene resin pellets were charged into a conical dryer and heated under reduced pressure while blowing nitrogen, the outgas amount of the product resin was significantly reduced from that of the raw material resin, and after 24 hours of treatment, the outgas of the raw material resin was reduced. Resin pellets having an amount of 2% or less of the amount and an outgas of 25 ppm by weight or less are obtained.

  According to the method for producing a low outgas resin of the present invention, a simple operation of charging a resin into a dryer having a stirring function and heating while blowing the gas, there is no fear of thermal degradation due to melting of the resin, and the resin is originally The outgas amount can be reduced while maintaining the good physical properties. The low outgas resin produced by the method of the present invention is useful as a raw material for plastic products used in a clean room, a coating material for electric wires and cables used in a clean room, and a raw material for food containers. Polyvinyl chloride resin having an outgas amount of 5 ppm by weight or less, polyethylene resin having 25 ppm by weight or less, and hydrogenated styrene thermoplastic elastomer having 5 ppm by weight or less produced by the method of the present invention are particularly useful as these raw materials. .

It is a systematic diagram of the one aspect | mode of the apparatus used for this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nitrogen introduction part 2 Vacuum line 3 Steam introduction part 4 Drain discharge pipe 5 Blowing nozzle 6 Blowing nozzle 7 Suction port 8 Conical container (conical dryer)

Claims (10)

  A method for producing a low-outgas resin, comprising charging a resin into a dryer having a stirring function and heating the resin while blowing the gas.   The method for producing a low outgas resin according to claim 1, wherein the inside of the dryer is depressurized to 101 to 1 kPa.   The method for producing a low outgas resin according to claim 1, wherein the amount of gas blown is 1 to 16 L (standard state) / min per kg of the resin.   The method for producing a low outgas resin according to claim 1, wherein gas is blown into the resin layer in the dryer.   The method for producing a low outgas resin according to claim 1, wherein the dryer having a stirring function is a conical dryer.   The method for producing a low outgas resin according to any one of claims 1 to 5, wherein the gas is nitrogen.   The method for producing a low outgas resin according to any one of claims 1 to 5, wherein the amount of residual organic matter in the resin is 1,000 ppm by weight or less.   A vinyl chloride resin produced by the method according to any one of claims 1 to 7, wherein an outgas amount is 5 ppm by weight or less.   A polyethylene resin produced by the method according to any one of claims 1 to 7, wherein an outgas amount is 25 ppm by weight or less.   A hydrogenated styrenic thermoplastic elastomer produced by the method according to any one of claims 1 to 7, wherein the amount of outgas is 5 ppm by weight or less.

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