JPH0737026B2 - Resin pellet manufacturing method - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing resin pellets, and more specifically, a resin having excellent blocking resistance despite being made of an adhesive resin such as ethylene-vinyl acetate copolymer. The present invention relates to a method for manufacturing pellets.

Technical background of the invention and its problems. Generally, ethylene and polar vinyl compounds such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer. In the copolymer with, since the tackiness increases as the content of the polar vinyl compound increases, there is a problem that the resin pellets block each other.

Conventionally, various treatment methods have been proposed as methods for preventing the blocking of the resin pellets. For example,
Inorganic powder such as talc and silica, powdered polyethylene, polyethylene wax, ethylene-vinyl acetate copolymer dispersion, or fine powder of ethylene-vinyl acetate copolymer saponified product is used as a resin pellet surface of the ethylene copolymer. Has been proposed, more specifically, a method of spraying a fine powder for coating on resin pellets,
Simple methods such as impregnating resin pellets into a fine powder slurry are shown.

However, in order to carry out the above method on an industrial scale, there was a problem that had to be solved. That is, on an industrial scale, it is required that the resin pellets be stored in a large-capacity hopper because it is necessary to carry out operations such as bagging with a continuous and simple operation.

However, in the simple method as described above, resin pellets coated with fine powder are suddenly put in a large-capacity hopper, and even if they are to be stored as they are, resin pellets themselves cause blocking due to the weight of the resin pellets. There was a problem that the resin pellets had to be stored in a hopper with a small capacity.

Therefore, the present inventors have conducted extensive studies to establish a method for producing resin pellets capable of storing a large amount of resin pellets made of an adhesive resin such as an ethylene copolymer in a large-capacity hopper. The surface of the resin pellets obtained by extruding the adhesive resin such as the system copolymer from the extruder and cutting it into pellets in water is coated with the anti-adhesion powder such as silica powder, and then the resin pellets are transferred to the hopper. While transporting, and then supplying gas into the hopper, a part of the resin pellets can be extracted from the lower part of the hopper and introduced into the hopper again from the upper part of the hopper so that drying can be performed while circulating the resin pellets. Therefore, it was found that blocking does not occur even if a large amount of resin pellets are stored in a large-capacity hopper, leading to the completion of the present invention. .

OBJECT OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and is a resin pellet comprising an adhesive resin such as ethylene-vinyl acetate copolymer, which has a large capacity. It is an object of the present invention to provide a method for producing resin pellets that does not cause blocking even if a large amount of resin pellets are stored in a hopper.

SUMMARY OF THE INVENTION The first method for producing resin pellets according to the present invention is a method in which an adhesive resin is extruded from an extruder and cut into pellets in water,
After coating the resin pellet surface with the powder for anti-adhesion, the resin pellet is introduced into the transportation pipe, and gas is fed into the transportation pipe to convey the resin pellet to the hopper,
Next, while supplying gas into the hopper, a part of the resin pellets is extracted from the lower part of the hopper and introduced again into the hopper from the upper part of the hopper, so that the resin pellets are dried while circulating. There is.

A second method for producing resin pellets according to the present invention is a method in which an adhesive resin is extruded from an extruder and cut into pellets in water, and then the resin pellets are introduced into a transportation pipe, and an adhesion-preventing powder slurry is introduced into the transportation pipe. By coating the surface of the resin pellets with anti-adhesion powder, by feeding gas into the transport pipe to transport the resin pellets to a hopper, and then while supplying gas into the hopper, It is characterized in that the resin pellets are circulated and dried so that a part of the resin pellets is extracted from the lower part of the hopper and is introduced into the hopper again from the upper part of the hopper.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the first and second resin pellet manufacturing methods according to the present invention will be specifically described with reference to FIG.

FIG. 1 is a schematic view showing the manufacturing steps in the first and second resin pellet manufacturing methods according to the present invention.

First, a method for manufacturing a first resin pellet according to the present invention will be described.

Specific examples of the adhesive resin used in the present invention include:
Ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid-acrylic acid Highly sticky ethylene-α-olefin copolymers such as copolymers of ethylene and polar vinyl compounds such as ester copolymers, ethylene-propylene copolymers and ethylene-1-butene copolymers are used. . For example,
As the ethylene-polar vinyl compound copolymer, a copolymer having a polar vinyl content of 25 to 60% by weight can be mentioned as a typical example.

In the present invention, in order to cut smoothly, the adhesive resin is extruded from the extruder 1 and then cut into pellets while being cooled in water.

The size of the resin pellet is preferably 2 to 5 mm. If the size of the resin pellets is too small, the blocking resistance of the resin pellets tends to deteriorate, while if the size of the resin pellets is too large, it takes time to purge the volatile components contained in the resin pellets. Therefore, it is not preferable. The cut resin pellets are drained by a drainer such as a fallout box 2 and a Simon Carter 3, and then the resin pellets are screened by an oversize screen (classifier) 4 and stored in a small hopper 5. To do.

The resin pellets temporarily put in the small hopper 5 are
It is transferred to the large capacity hopper 8 through the transport pipe 6. At this time, in the first invention, the resin pellets are coated with the adhesion preventing powder before being introduced into the transport pipe 6.

In the present invention, various methods can be adopted as a coating method of the anti-adhesion powder, but from the viewpoint of uniformly adhering the anti-adhesion powder and simplifying the manufacturing process, a powder slurry is used. The method is preferred. For example, the cut pellets are introduced into a slurry tank equipped with a stirrer in which an aqueous dispersion of anti-adhesion powder is stored in advance and coated, and then immediately introduced into a centrifugal dehydrator such as a Simon Carter to drain water, thereby removing the resin pellet surface. For example, a method of uniformly coating the anti-adhesion powder with the adhesive can be used.

As the adhesion-preventing powder used for coating the resin pellet surface in the present invention, specifically, kaolinite,
Clays such as pyrophyllite, inorganic powders such as talc, mica, silica sand, shirasu, magnesium carbonate and calcium carbonate, organic powders such as polyethylene wax and EVA are used, and silica powder is preferably used. These anti-adhesion powders usually have an average particle size of
The thickness is 0.001 to 30 μm, preferably 0.005 to 1 μm. If the average particle diameter of the anti-adhesion powder is less than 0.001 μm, it is not preferable because the anti-adhesion fine powders are likely to aggregate with each other. On the other hand, if the average particle diameter of the anti-adhesion powder exceeds 30 μm, It is not preferable because the adhesion with the surface of the resin pellet is deteriorated and the anti-adhesion powder is easily peeled off during transportation by piping.

The anti-adhesion powder slurry used in the present invention,
A slurry having a concentration of about 50 to 300 g / l is preferable.

The amount of adhesion preventing powder adhering to the surface of the resin pellet is usually 500 to 5000 ppm.

A resin pellet coated with an anti-adhesion powder such as silica powder is introduced into the transportation pipe 6, and a gas, preferably air or a gas such as nitrogen gas, is sent into the transportation pipe 6 by a blower 7 to make the resin pellet of a large volume. Transport to a hopper 8, for example a hopper for 10 to 100 tons.

At this time, when air is used as the carrier gas, air having a flow rate of about 20 to 100 m ³ / min may be used.

Next, a gas, preferably air having a temperature of about 15 to 25 ° C. that has been cooled and dehumidified through a filter 16, a blower 10, and a cooling dehumidifier 9.
Gas such as nitrogen gas is supplied to the large-capacity hopper 8, while a part of the resin pellets is extracted from the lower part of the hopper 8 and introduced into the hopper 8 from the upper part of the hopper 8, preferably a gas. A gas such as air and nitrogen gas at about 15 to 25 ° C., which has been cooled and dehumidified through the filter 17, the blower 12 and the cooling dehumidifier 11, is supplied to the blend line 13 and dried while circulating the resin pellets.

At this time, if the supply speed of the resin pellets supplied to the large-capacity hopper 8 is, for example, 2 to 20 tons / hour, the circulation speed of the resin pellets partially extracted from the lower part of the hopper 8 and circulated to the upper part of the hopper 8. Is about 1/5 to 2/3 of the resin pellet supply rate, for example, dehumidified air having a flow rate of 20 to 100 m ³ / min may be used as the gas for conveying the resin pellets.

In the present invention, the supply port of the gas into the hopper 8 is mainly provided in the lower part of the hopper 8, but the supply port may be provided in the upper part of the hopper 8.

As described above, while supplying gas into the hopper 8,
By circulating resin pellets whose surface is coated with anti-adhesion powder such as silica powder, water and monomers adhering to the resin pellets can be released to the outside of the system to keep the resin pellets dry. it can.
Therefore, even when a large amount of resin pellets are stored in the large capacity hopper 8, blocking can be prevented.

The resin pellets stored in the large-capacity hopper 8 are packaged into a product through a packaging process 14.

Next, a method for manufacturing the second resin pellet according to the present invention will be described.

As the adhesive resin used in the present invention, the same ethylene-based copolymer as the adhesive resin used in the first method for producing a resin pellet according to the present invention is used.

In the above-described first method for producing resin pellets according to the present invention, the surface of the resin pellets is coated with an anti-adhesion powder such as silica powder before the resin pellets are introduced into the transport pipe. In the resin pellets of No. 3, the resin pellets in the hopper 5 are introduced into the transportation pipe 6, and the slurry pump 15 is used to introduce the adhesion preventing powder slurry such as silica powder slurry into the resin pipe. Coat the pellet surface with anti-sticking powder.

The average particle diameter of the anti-adhesion powder contained in the anti-adhesion powder slurry such as silica powder slurry used in the second resin pellet production method of the present invention is the above-mentioned first resin pellet of the present invention. This is the same as in the manufacturing method of. The mixture ratio of the anti-adhesion powder and water in the anti-adhesion powder slurry is usually 250 to 2000 parts by weight with respect to 100 parts by weight of the anti-adhesion powder.

The manufacturing process other than the above in the second resin pellet manufacturing method according to the present invention is the same as the manufacturing process in the first resin pellet manufacturing method according to the present invention described above.

Effects of the Invention In the method for producing a resin pellet according to the present invention, on the surface of a resin pellet obtained by extruding an adhesive resin such as an ethylene copolymer from an extruder and cutting it into pellets in water,
After coating with anti-adhesion powder such as silica powder, convey the resin pellets to the hopper, then
While supplying gas into the hopper, a part of the resin pellets is extracted from the lower part of the hopper and is introduced into the hopper again from the upper part of the hopper so that the resin pellets are dried while being circulated. Has excellent blocking resistance, and has an effect that blocking does not occur even if a large amount of resin pellets are stored in a large-capacity hopper. Therefore, according to the present invention, since a large-capacity hopper can be used for storing resin pellets made of an adhesive resin, it is not necessary to prepare many small-capacity hoppers.

Further, the resin pellets obtained by the production method according to the present invention are packed in a sufficiently dried state to be manufactured into a product, so that the resin pellets do not block each other in the bag.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

First, the methods for evaluating blocking resistance in Examples and Comparative Examples are shown below.

Blocking resistance evaluation method A cylindrical container with an inner diameter of 40 mm and a height of 70 mm was charged with resin pellets coated with a certain amount of anti-adhesive agent on the pellet surface, and a 4.1 kg load was placed on the resin pellets in an atmosphere of a predetermined temperature. Put on. The load is then removed and the cylinder is inverted and the time taken for all the resin pellets to flow out of the cylinder is recorded. This test was repeated by gradually raising the temperature, and the maximum temperature at which 100% of the resin pellets were discharged per minute was called the stick temperature, and the blocking resistance of the coated resin pellets was used as a guide. It was judged based on the following criteria.

Stick temperature Rank 20 ° C. or higher A 10 ° C. to less than 20 ° C. B 0 ° C. to less than 10 ° C. C-10 ° C. to less than 0 ° C. D less than 10 ° C. E Example 1 Adhesive resin ethylene-vinyl acetate copolymer ( EVA
−1: VA 41% by weight, MFR 65 dg / min) was extruded from the extruder 1 and then cut into pellets while cooling in water. Then, cut the resin pellets immediately, in advance, the average particle size
High-purity (SiO ₂ 99.8% or more) ultrafine silica of 10 mμ is dispersed in water using a high-speed stirrer and led to a silica water dispersion tank where the solid content concentration is adjusted to 10% by weight, and the resin pellet surface is treated with silica powder. After coating, it was carried to a draining device such as a fallout box 2 and a Simon Carter 3 to drain the resin pellets, which were then screened with an oversize screen 4 and stocked in a small hopper 5.

The silica-coated resin pellets temporarily stocked in the small hopper were introduced into the transport pipe 6, and the blower 7
It was conveyed to the large capacity hopper 8 together with the air.

Then, while the air at 17 ° C. dehumidified by the cooling dehumidifier 9 is supplied to the large-capacity hopper 8 using the blower 10, a part of the resin pellets is extracted from the lower part of the hopper 8 and the upper part of the hopper 8 is extracted. Introduced into the hopper 8 again,
Air having a temperature of 17 ° C. was dehumidified by the cooling dehumidifier 11 using a blower 12 at a flow rate of 50 m ³ / min to the blend line 13, and was dried while circulating the silica-coated resin pellets. The dried resin pellets stored in the large-capacity hopper 8 were packaged into a product through a packaging process 14.

The silica adhesion amount of the resin pellet thus obtained was 1000 ppm. The sticking temperature of this coating resin pellet was 15 ° C., and the blocking resistance was evaluated as B rank.

Example 2 Product resin pellets were obtained in the same manner as in Example 1 except that the solid content concentration of the ultrafine particle silica was changed to 20% by weight. The silica adhesion amount of the resin pellets thus obtained was 2000 ppm. The stick temperature of this resin pellet was 25 ° C., and the blocking resistance was evaluated to rank A.

Example 3 Product resin pellets were obtained in the same manner as in Example 1, except that the solid content concentration of the ultrafine particle silica was changed to 5% by weight. The silica adhesion amount of the resin pellets thus obtained was 500 ppm. The stick temperature of this resin pellet was 10 ° C, and the evaluation of blocking resistance was B rank.

Example 4 In Example 1, the silica powder has an average particle diameter of 30 m.
Product resin pellets were obtained in the same manner as in Example 1 except that µ silica powder was used. The silica adhesion amount of the resin pellets thus obtained was 900 ppm. Also,
The stick temperature of this resin pellet was 17 ° C., and the evaluation of blocking resistance was B rank.

Example 5 In Example 1, ethylene-vinyl acetate copolymer (EV
A-1) instead of ethylene, which has strong pellet adhesion
Vinyl acetate copolymer (EVA-2: VA45% by weight, MFR90dg / mi
n) is used, and silica having an average particle size of 30 mμ is used as the high-purity ultrafine particle silica, and the solid content concentration of the ultrafine particle silica in the silica / water dispersion liquid is set to 15% by weight. As a result, product resin pellets were obtained.
The silica adhesion amount of the resin pellets thus obtained is
It was 1500 ppm. The stick temperature of this resin pellet was 10 ° C, and the evaluation of blocking resistance was B rank.

Example 6 In Example 1, instead of the silica-water dispersion liquid, talc having an average particle size of 1.5μ and a small amount of anionic surfactant were added to water and dispersed in a high-speed stirrer to obtain a solid content concentration of 5 Use the talc / water dispersion adjusted to wt% and replace the ethylene-vinyl acetate copolymer (EVA-1) with an ethylene-vinyl acetate copolymer (EVA-2:, VA45 wt. %, MFR 90 dg / min), and product resin pellets were obtained in the same manner as in Example 1. The amount of talc deposited on the resin pellets thus obtained was 1000 ppm. Further, the stick temperature of this resin pellet is 5 ° C., and the evaluation of blocking resistance is
It was C rank.

Example 7 In Example 6, instead of talc, the average particle size was 2 μm.
Product resin pellets were obtained in the same manner as in Example 6 except that the above clay was used. The amount of clay adhering to the resin pellets thus obtained was 800 ppm. The stick temperature of this resin pellet was 5 ° C., and the evaluation of blocking resistance was C rank.

Example 8 In Example 1, ethylene-vinyl acetate copolymer (EV
Product resin pellets were obtained in the same manner as in Example 1 except that a sticky ethylene-ethyl acrylate copolymer (EEA-1, EA41 wt%, MFR8 dg / min) was used instead of A-1). Got The silica adhesion amount of the resin pellets thus obtained was 900 ppm. The stick temperature of this resin pellet was 17 ° C., and the evaluation of blocking resistance was B rank.

Example 9 Adhesive resin ethylene-vinyl acetate copolymer (EVA-
After 1) was extruded from the extruder 1, it was cut into pellets while cooling in water. Next, the cut pellets were immediately conveyed to a draining device such as a fallout box 2 and a Simon Carter 3 to drain the resin pellets, and then the resin pellets were screened by an oversize screen 4 and stocked in a small hopper 5.

Resin pellets temporarily stocked in a small hopper,
It is introduced into the transport pipe 6 and the slurry pump 15 is introduced into the transport pipe 6.
Using a high-speed stirrer, high-purity ultrafine silica particles with an average particle size of 10 mμ are dispersed in water beforehand to obtain a solid content concentration.
By introducing a silica / water dispersion liquid adjusted to 10% by weight, the surface of the resin pellets is coated with silica fine powder, and the blower 7 and the large capacity hopper 8 together with the air.
Was transported. Thereafter, the same procedure as in Example 1 was carried out to obtain product resin pellets. The amount of silica attached to the resin pellets thus obtained was 1100 ppm. The stick temperature of this resin pellet was 16 ° C., and the blocking resistance was rated B.

Comparative Example 1 In the same manner as in Example 1 except that the surface of the resin pellet was not coated with silica powder,
A product resin pellet was obtained. The resin pellets thus obtained had a sticking temperature of -10 ° C and a blocking resistance of D rank.

Comparative Example 2 In Example 1, the ethylene-vinyl acetate copolymer (EV
Instead of A-1), ethylene-vinyl acetate copolymer (E
Product resin pellets were obtained in the same manner as in Example 1 except that VA-2) was used and the surface of the resin pellets was not coated with silica powder. The resin pellets thus obtained had a sticking temperature of -15 ° C, and the blocking resistance was rated E.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing step in the first and second resin pellet manufacturing methods according to the present invention. 1 ... Extruder, 2 ... Fallout box 3 ... Simon Carter 4 ... Oversize screen 5 ... Small hopper, 6 ... Transport tube 7 ... Blower, 8 ... Large capacity hopper 9 ... Cooling dehumidifier, 10 ... Blower 11 ... Cooling dehumidification Container, 12 ... Blower 13 ... Blend line, 14 ... Bagging process 15 ... Slurry pump

Claims (2)

[Claims] 1. An adhesive resin is extruded from an extruder and cut into pellets in water, the surface of the resin pellets is coated with an anti-adhesion powder, and then the resin pellets are introduced into a transportation pipe, and a gas is introduced into the transportation pipe. To convey the resin pellets to a hopper, and then while supplying gas into the hopper, while extracting a part of the resin pellets from the lower portion of the hopper and introducing the resin pellets into the hopper from the upper portion of the hopper, A method for producing resin pellets, which comprises drying the resin pellets while circulating them. 2. A resin pellet surface is obtained by extruding an adhesive resin from an extruder and cutting it into pellets in water, introducing the resin pellet into a transportation pipe, and introducing a powder slurry for preventing adhesion into the transportation pipe. While coating with a powder for anti-adhesion, the gas is sent into the transport pipe to convey the resin pellets to a hopper, and then the gas is supplied into the hopper while a part of the resin pellets is fed from the lower part of the hopper. A method for producing resin pellets, characterized in that the resin pellets are dried while being circulated so as to be extracted and introduced into the hopper from above the hopper again.