JP3045365B2 - Soft polyolefin resin granules and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granulated flexible polyolefin resin having improved surface tackiness. More specifically, it is intended to provide a granulated body which does not block during storage of the granulated body by improving the surface tackiness of the soft polyolefin resin granulated body.

[0002]

2. Description of the Related Art Soft polyolefin resin is a soft chlorinated resin that has social problems such as toxicity and transfer due to bleed out of plasticizer and monomer, and acid rain due to generation of hydrogen chloride during incineration. Used as a substitute for vinyl resin, it has no pollution, flexibility, mechanical strength,
It has features such as excellent transparency. From this point, the soft polyolefin resin is preferably used as a soft film raw material, various hot melt resin raw materials and the like. However, since the soft polyolefin resin contains a large amount of an amorphous component having a relatively low molecular weight, the surface adhesion of the granules is strong, and the blocking is severe during granulation and storage of the granules. There were problems such as difficulty in removing the granules, which hindered the supply to the extruder. For this reason, a method of adhering powder particles to the surface of the granulated material (Japanese Patent Laid-Open No. 58-6923)
No. 8, JP-A-1-317709) and the like have been studied. However, even with these methods, the effect is not sufficient, or when the powder particles adhered to the surface of the granule use the granule as a raw material for forming a film, a sheet, etc., the properties such as the transparency of the molded body are adversely affected. And other problems.

[0003]

SUMMARY OF THE INVENTION The present invention provides a soft polyolefin resin granule which has improved surface tackiness of a soft polyolefin resin granule and does not block the granule.

[0004]

The soft polyolefin resin of the present invention preferably has a heat of crystal fusion in the range of 10 to 80 Joule / g. If it is less than 10 Joule / g, the crystallinity is too low and a clear spherulite structure cannot be obtained. If it is larger than 80 Joule / g, the crystallinity is too high, and the resin lacks flexibility and cannot be said to be a soft polyolefin resin. The soft polyolefin resin of the present invention may be produced at a time in the polymerization step, or may be produced by blending a substantially amorphous polyolefin and a crystalline polyolefin so that the heat of crystal fusion falls within the above range. Good. As a method of producing at once in the polymerization stage, known techniques, for example, Ziegler-N comprising a transition metal compound and an organometallic compound
ethylene, propylene, butene
1. Production of α-olefin homopolymers, copolymers, terpolymers, etc., such as 1, pentene-1, hexene-1, heptene-1, octene-1, etc. in gas phase, bulk, slurry and solution. Method. As a method for adjusting the heat of crystal fusion to be within the above range, this is also a known method, the type of the catalyst component, the amount used, the amount of the electron donor added,
It is easily achieved by changing the polymerization temperature and pressure. The heat of crystal fusion was measured as follows. DSC-5 manufactured by Shimadzu Corporation as a differential scanning calorimeter
Using 0, the sample amount was about 10 mg, the measurement atmosphere was a nitrogen atmosphere, and indium was used as a calorimetric standard. The heating program first heated the sample to 210 ° C. at a rate of 50 ° C./min, left it at 210 ° C. for 5 minutes,
Cool to -42 ° C at a cooling rate of ° C / min and leave at -42 ° C for 5 minutes. Thereafter, the measurement was performed from -40 ° C to 200 ° C at a heating rate of 20 ° C / min. The heat of crystal fusion was calculated using a straight line obtained by directly extrapolating the specific heat curve of the sample in a completely molten state to the low temperature side as a baseline. When the amorphous polyolefin and the crystalline polyolefin are blended as another method for producing the soft polyolefin resin used in the present invention, a composition of the amorphous polyolefin and the crystalline polypropylene is preferably used. The above-mentioned amorphous polyolefin refers to a boiling n-heptane insoluble content, that is, boiling n
-Soxhlet extraction by heptane 70% by weight insoluble matter
Or less, preferably 60% by weight or less. Boiling n
-When the heptane-insoluble content is more than 70% by weight, the ratio of the amorphous portion is reduced, and the polymer lacks flexibility and does not exhibit characteristics as a soft polyolefin. As the amorphous polyolefin, those having a number average molecular weight of 20,000 or less having a large content of low molecular weight components are particularly preferably applied. As the amorphous polyolefin used in the present invention, for example, amorphous polypropylene, a copolymer of amorphous propylene and another α-olefin, or the like can be used. For example, atactic polypropylene by-produced during the production of crystalline polypropylene may be used, or may be produced from raw materials and used. In the case of target production, for example, it can be obtained by polymerizing a raw material monomer in the presence of hydrogen and / or in the absence of hydrogen using a titanium-supported catalyst supported on magnesium chloride and triethylaluminum. From the viewpoint of the stability of raw material supply and the stability of quality, it is preferable to use a predetermined amorphous polyolefin produced for the purpose. In addition, if there is a corresponding suitable commercial product, a commercial product can be appropriately selected and used.

Specific examples of the amorphous polyolefin of the present invention include polypropylene, propylene / ethylene copolymer, propylene / butene-1 copolymer, and propylene / propylene copolymer.
Butene-1 / ethylene-3 terpolymer, propylene / hexene-1 / octene-1 / 3 terpolymer, propylene / hexene-1 / 4-methylpentene-1 / 3 terpolymer, polybutene-1 And the like. As the crystalline polyolefin to be mixed with the amorphous polyolefin, crystalline polypropylene is preferably used because of its compatibility with the amorphous polyolefin.

The crystalline polypropylene used in the present invention includes polypropylene which is generally commercially available for extrusion molding, injection molding, blow molding and the like, and refers to isotactic polypropylene insoluble in boiling n-heptane.
In this case, a propylene homopolymer may be used, or a copolymer of isotactic polypropylene having stereoregularity and another α-olefin may be used. The crystalline polypropylene may be a commercially available product, or may be manufactured and used. The production of crystalline polypropylene
It is not particularly limited, and can be appropriately selected from conventional methods for producing crystalline polypropylene and applied.

The α-olefin used for copolymerization with crystalline polypropylene includes α-olefins having 2 to 8 carbon atoms.
-Olefins such as ethylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1 and the like are preferred. Among these, ethylene or butene-1 is particularly preferable.

In the present invention, the crystalline polypropylene is preferably a propylene homopolymer, a propylene / ethylene random copolymer or a block copolymer having an ethylene component of 30% by weight or less, preferably 1 to 25% by weight. And a random copolymer or block copolymer of propylene / butene-1 containing 20% by weight or less of butene-1. The crystalline polypropylene can be used alone or in combination of two or more.

Further, the amorphous polyolefin and / or crystalline polypropylene in the present invention may be modified. The above-mentioned amorphous polyolefin and / or crystalline polypropylene can be used, for example, in the presence of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid and / or their esters, acid anhydrides And a derivative thereof such as a metal salt. Among these modified products, those modified with maleic anhydride and itaconic anhydride are preferably used, and those modified with maleic anhydride are more preferably used.

In the present invention, a method for preparing a soft polyolefin comprising a composition of an amorphous polyolefin and a crystalline polyolefin may be a conventionally used method, for example, a kneader such as a kneader, a Banbury mixer, or a roll.
Heat melting and kneading can be performed using a single screw or twin screw extruder or the like. In addition, adjustment of soft polyolefin
It may be adjusted in advance before the granulation operation according to the present invention, or may be performed simultaneously with the granulation operation according to the present invention. As described above, the amorphous polyolefin and the crystalline polypropylene have a heat of crystal fusion of 10 to 80 Jou.
It is sufficient that the composition be in the range of le / g, but it is particularly preferable that the composition is composed of 20 to 80% by weight of the amorphous polyolefin and 80 to 20% by weight of the crystalline polypropylene. If the proportion of the amorphous polyolefin is less than 20% by weight, the flexibility is insufficient and the characteristics as a soft polyolefin are not exhibited. When the proportion of the amorphous polyolefin is more than 80% by weight, the proportion of the amorphous component having a relatively low molecular weight in the composition becomes too large, and the method of the present invention sufficiently improves the surface tackiness of the granulated product. Can not do.

In the present invention, it is preferable that the crystallization nucleating agent is blended in the soft polyolefin resin, because the effect of improving the surface tackiness of the granulated product is further increased. Examples of the crystallization nucleating agent to be blended in the present invention include organic acids and derivatives thereof, sorbitol derivatives, various pigments, and fine powders of inorganic substances. Organic acids and their derivatives, sorbitol derivatives, various pigments, and inorganic fine powders are used alone or in combination. Specific examples of organic acids and derivatives thereof include succinic acid, glutaric acid, adipic acid, speric acid,
Sebacic acid, salicylic acid, thioglycolic acid, benzoic acid, P-isopropyl, P-tert-butylbenzoic acid, diphenylacetic acid, monophenylacetic acid, phenyldimethylacetic acid and the like. Specific examples of the organic acid derivative include a sodium salt of benzoic acid, an aluminum salt of benzoic acid, an aluminum salt of P-tert-butylbenzoic acid,
Examples include calcium salts of adipic acid, amine salts of benzoic acid or β-phenylacetic acid, and sodium salts of glutamic acid. Sorbitol derivatives include dibenzylidene sorbitol, and various pigments include rutile titanium, Cd
There are inorganic and phthalocyanine-based and quinacridone-based organic pigments such as red, channel carbon, iron oxide, cyanine blue, cyanine green, and polyazo yellow. Examples of the inorganic fine powder include talc and hydrotalcite salt. Examples of the combination of an organic acid or an organic acid salt with another compound include a combination of phthalic acid, phthalic anhydride, calcium stearate, and barium.

The crystallization nucleating agent of the present invention is used in an amount of 0.01 to 2% by weight, preferably 0.02 to 1% by weight, based on the soft polyolefin resin. If it is less than 0.01% by weight, the effect of improving the surface tackiness of the granules is small. If the content exceeds 2% by weight, the effect of improving the surface tackiness does not change, but rather, it causes problems such as bleed out of the crystallization nucleating agent itself and increases the cost, which is not preferable. Examples of the method for melting the soft polyolefin resin include a kneader such as a kneader, a Banbury mixer, and a roll, and a single-screw or twin-screw extruder. When a soft polyolefin resin containing a crystalline portion is cooled and solidified from a molten state, the soft polyolefin resin generally has a spherulite structure. When cooling and solidifying a soft polyolefin resin in the molten state,
In the conventional method, the molten soft polyolefin resin is generally cooled and solidified in a water bath having a water temperature of 5 to 30 ° C. and granulated. In this case, the portion of the molten soft polyolefin resin that comes into contact with the cooling water at the above temperature is rapidly cooled and solidified, and the portion that is not in direct contact with the cooling water is cooled and solidified more slowly than it and granulated. As a result, when viewed in the cross-sectional direction of the granule, the average spherulite diameter of the rapidly cooled and solidified surface portion becomes smaller, and the average spherulite diameter of the cooled and solidified central portion becomes larger than that. The ratio of the average spherulite diameter of the central part to the average spherulite diameter of the surface layer part in the cross-sectional direction of the soft polyolefin resin granules obtained by the conventional method obtained from observation with a polarizing microscope or a scanning electron microscope. Is greater than 10/1. Granules having a large difference in spherulite diameter, having a ratio of the average spherulite diameter of the central part and the surface part in such a range,
Surface tackiness was large, and blocking during storage of the granules was a problem. As the cause, as seen in the difference in the average spherulite diameter between the surface layer and the central part of the granulated body, the granulated body has not reached a stable state as a structure and has been stored after manufacturing the granulated body. It is presumed that a relatively low molecular weight amorphous component in the soft polyolefin resin migrates to the surface of the granule due to the action of trying to take a stable structure. As a result of various investigations to improve such a soft polyolefin resin granule having a large surface tackiness, the ratio of the average spherulite diameter in the center part of the granule to the average spherulite diameter in the surface layer part was 10/1 or less, It has been found that if the ratio is preferably 5/1 or less, the surface tackiness of the granulated body can be prevented, and the present invention has been completed. If the ratio of the average spherulite diameter at the center of the granules to the average spherulite diameter at the surface layer is 10/1 or less, the structure of the soft polyolefin resin granules becomes a stable structure, and the surface adhesion of the granules It is estimated that the properties are improved and blocking during storage of the granules can be prevented. As a method for granulating a soft polyolefin resin having such an average spherulite diameter ratio, there is a method in which a soft polyolefin resin in a molten state is gradually cooled and solidified to form a granule. in this case,
When the crystallization nucleating agent is added to the soft polyolefin resin, the ratio of the average spherulite diameter can be made smaller, and the effect of improving the surface tackiness becomes higher. The average spherulite diameter was calculated as follows. The cross-sectional direction of the soft polyolefin resin granule is a cut surface that connects the most rapidly cooled surface and the most slowly cooled center. For example, in the case of a cylindrical pellet obtained by cutting a strand, a cross section perpendicular to the extrusion direction has a substantially circular cross section. In hot-cut spherical pellets, it is the cut surface of the thickest part. For the measurement, a slice sample of this section was cut out, and the slice section was used as an observation sample. The central part in the granule cross-sectional direction is approximately 0.3 from the center of the circular or elliptical section.
mm (1/10 or less of the cross-sectional diameter). The surface portion of the cross section indicates a range of about 0.3 mm from the outer periphery of the cross section. Four observation fields of 0.1 mm square from the central part and the surface part were set as observation targets. Observation of the spherulite diameter was performed with a polarizing microscope and / or an electron microscope according to the size of the spherulite diameter, and the average value of the spherulite diameters in the visual field was determined by image processing. In the image processing, each spherulite was approximated to a circle, and its diameter was defined as the spherulite diameter. The total average value in four visual fields was determined and defined as the average spherulite diameter. As a method for slowly cooling and solidifying and granulating a soft polyolefin resin in a molten state, for example, when it is melted by a single-screw or twin-screw extruder, the molten extrudate is directly cooled and solidified in the air and then cut, or water at 40 ° C. or more Or a method of cutting a strand that has been cooled and solidified in a water temperature of 40 ° C. or higher. At this time, if the water temperature at the time of hot cutting and the water temperature at the time of strand cutting are lower than 40 ° C., a sufficient slow cooling effect cannot be obtained, and the average spherulite diameter in the central portion of the manufactured granules and the average in the surface layer portion are not obtained. The ratio of the spherulite diameter becomes larger than 10/1, and the surface tackiness of the granules is not improved. The effect of improving the surface tackiness is more effective as the cooling water temperature is higher. However, if the temperature is too close to the melting point of the soft polyolefin resin, the solidification rate becomes too slow, which is not preferable. Also, after melting with a kneader such as a kneader, Banbury mixer, roll, etc., it is compressed into a sheet, cooled and solidified in the air, or immersed in water at 40 ° C. or higher, and solidified. Into granules.

The granulation method by the hot cut (underwater cut) method will be described in more detail. The resin discharged from the extruder is extruded from an annular die hole and cut by a rotary blade in a cutting chamber. In the cutting chamber, water whose temperature is controlled by a water circulation device is circulated through a piping line, and the pellets cut in the cutting chamber are conveyed while being cooled and solidified at this constant temperature. In the present invention, if the water temperature at this time is 40 ° C. or higher, the ratio of the average spherulite diameter in the center portion of the manufactured granules to the average spherulite diameter in the surface layer portion is 10 /.
The effect of improving the surface tackiness of the obtained pellets is 1 or less. In the case of the strand cutting method, a strand extruded from a discharge port of an extruder is cooled in air or a water tank, and then cut by a strand cutter to obtain pellets. In the present invention, if the strand is cooled at this time by air cooling or in a water tank whose temperature is controlled to 40 ° C. or higher, the effect of improving the surface tackiness of the obtained pellets is large.

[0014]

The soft polyolefin resin granules of the present invention have improved surface tackiness, do not block during storage, and fall smoothly even when put into the hopper of a molding machine, and are easy to handle. is there.

[0015]

[Examples and Comparative Examples]

Example 1 A propylene / butene-1 copolymer (trade name: REXTAC RT2780, manufactured by Lexen USA, a weight ratio of propylene / butene-1 was 65 /
35, number average molecular weight 6500). A material obtained by melt-mixing crystalline polypropylene (trade name: B301H, manufactured by Ube Industries, Ltd.) and amorphous polyolefin at a weight ratio of 50/50 was used as a soft polyolefin resin raw material. The heat of fusion of the composition measured by the method described above was 34 Joule.
/ G. In addition, the insoluble content of this composition in Soxhlet extraction with boiling n-heptane was 32% by weight. Soxhlet extraction conditions: 200 ml of n-heptane was poured into 3 g of a film strip sample having a thickness of about 0.5 mm ^t and extraction was performed for 8 hours by a Soxhlet extractor. The extraction was performed based on the weight of the charged sample before and after the extraction operation. It was determined from the change in weight. The above soft polyolefin resin raw material was supplied from a hopper of a twin-screw extruder having a screw diameter of 30 mmφ, and was melt-kneaded. The molten soft polyolefin resin raw material is extruded into a strand at a resin temperature of 230 ° C. from the discharge port of the extruder, guided to a cooling bath (length 2 m) adjusted to a water temperature of 40 ° C., and gradually cooled and solidified. It was cut by a strand cutter and granulated into pellets. Pellets were obtained at 2 kg / h. The ratio of the average spherulite diameter at the center of the granules to the average spherulite diameter at the surface layer in the cross-sectional direction of the manufactured granules was determined by the above method. Next, the obtained pellet was left in an air atmosphere (gear oven) at a temperature of 40 ° C. Next, the pellets were taken out periodically and the blocking state of the pellets was observed. At the same time, the upper opening inner diameter 70mmφ,
In a frustum-shaped paper container with a lower opening inner diameter of 50 mmφ, 90
g and the time until all the pellets fell from the container was measured. The shorter the drop time, the lower the surface tackiness of the pellet. The display method of the observation result of the blocking state of the pellet is as follows. ：: no blocking at all △: slightly blocking ×: severely blocking Table 1 shows the results.

[0016]

[Table 1]

Examples 2 to 3 The same procedure as in Example 1 was carried out except that the water temperatures of the cooling tanks were set at 60 ° C. and 80 ° C., respectively.

Comparative Examples 1 and 2 The same procedure as in Example 1 was carried out except that the water temperatures of the cooling tanks were 30 ° C. and 20 ° C., respectively.

Example 4 The same soft polyolefin resin raw material as in Example 1 was used. After the soft polyolefin resin was melted in the same manner and under the same conditions as in Example 1, the resin temperature was changed to 230 through the discharge port of the extruder.
Strand extruded at a temperature of 23 ° C. in an air atmosphere (temperature 23
℃), then solidified by cooling with a strand cutter and pelletized. Evaluation was performed in the same manner as in Example 1.

Example 5 Crystalline polypropylene (trade name B, manufactured by Ube Industries, Ltd.)
301H) was supplied from a hopper of a twin-screw extruder having a screw diameter of 80 mmφ. Amorphous polyolefin (trade name
REXTAC RT2780 (manufactured by Lexen, USA) was previously heated to 190 ° C by a pre-melter (manufactured by Taiyo Giken).
After melting to ° C., the mixture was supplied from the intermediate opening of the twin-screw extruder through a transport pipe. By adjusting each feed rate, the weight ratio of crystalline polypropylene to amorphous polyolefin was 50/50. The soft polyolefin resin having the above composition melt-kneaded in the twin-screw extruder is extruded from the annular die holes at a resin temperature of 230 ° C. from the twin-screw extruder, and cut by an underwater cut pelletizing system (manufactured by Geller). It was cut by a rotating blade in the chamber. Water controlled at 60 ° C. is circulated in the cutting chamber and the transport line of the cut pellets by a water circulating device, and the cut pellets are transported while being gradually cooled and solidified in the circulating water, and are dried by a dryer section. After being dried, it was discharged and 80 kg / hour of granulated pellets were obtained. The obtained pellets were evaluated in the same manner as in Example 1.

Example 6 The same operation as in Example 5 was performed except that the circulating water temperature was set at 80 ° C.

Example 7 Crystalline polypropylene (trade name B, manufactured by Ube Industries, Ltd.)
301H) and an amorphous polyolefin (REXTAC RT2780, manufactured by Lexen, USA) having a composition of 4
What was melt-mixed so as to have a weight ratio of 0/60 was used as a soft polyolefin resin raw material. The heat of fusion of this composition was 27 Joule / g. The Soxhlet extraction insoluble content of this composition with boiling n-heptane was 26% by weight. The operation was performed in the same manner as in Example 1 except that the water temperature of the cooling tank was set to 60 ° C.

Comparative Example 3 The same procedure as in Example 7 was carried out except that the water temperature in the cooling bath was 30 ° C.

Example 8 Crystalline polypropylene (trade name B, manufactured by Ube Industries, Ltd.)
301H) and an amorphous polyolefin (trade name: REXTAC RT2780, manufactured by Lexen, USA) in a ratio of 50/5.
The crystallization nucleating agent dibenzylidene sorbitol (trade name: EC-1-55, manufactured by EC Chemical Co., Ltd.) was added to the soft polyolefin resin blended so as to have a weight ratio of 0.
5% by weight was added. Other than that, it carried out similarly to Example 1.

Example 9 The same operation as in Example 8 was carried out except that the water temperature in the cooling bath was set at 80 ° C.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-69238 (JP, A) JP-A-61-98736 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 3/00-3/28 C08L 1/00-101/16

Claims (5)

(57) [Claims] 1. A method according to claim 1, wherein the soft polyolefin resin is an amorphous polyolefin resin.
20 to 80% by weight of fins and 8 of crystalline polypropylene
0 to 20% by weight, wherein the ratio of the average spherulite diameter of the central part of the granules to the average spherulite diameter of the surface layer part is 10/1 or less in the cross-sectional direction of the soft polyolefin resin granules. Soft polyolefin resin granules. 2. The method of claim 1, wherein the amorphous polyolefin is a boiling n-hepta.
Soxhlet extraction insoluble content is 70% by weight or less,
It has a number average molecular weight of 20,000 or less
The soft polyolefin resin granulation according to claim 1, wherein
body. 3. The method of claim 1, wherein the amorphous polyolefin is polypropylene.
Propylene, ethylene copolymer, propylene bute
-1 copolymer, propylene / butene-1 / ethylene-
Terpolymer, propylene / hexene-1 / octene
1-3 terpolymer, propylene / hexene-1,4-me
Chilpentene-1 terpolymer, polybutene-1
The flexible polyole according to claim 1 or 2, wherein
Finned resin granules. 4. The soft polyolefin resin granule is melt-pressed.
Either cut the extrudate as it is in the air,
Hot cut in water at 40 ° C or higher, or
Cut strands cooled and solidified in water temperature of ℃ or more
It is solidified and granulated by a method.
4. The soft polyolefin resin granule according to 3. 5. The method according to claim 1, wherein the soft polyolefin resin has a heat of crystal fusion.
Soft polyolefin resin in the range of 10 to 80 Joule / g
The soft poly according to any one of claims 1 to 4,
Olefin resin granules.