Anti-blocking agent and method for producing resin pellets

Abstract

To provide: an anti-blocking agent capable of preventing blocking of resin pellets having adhesive properties, in particular, to uniformly and thinly adhere (coat) a small amount of anti-blocking agent onto a surface of resin such as soft olefin resins, and to provide an anti-blocking agent suitable for manufacturing resin pellets without reducing other product properties such as transparency; and a method for manufacturing resin pellets using the same.SOLUTION: An anti-blocking agent containing a group 2 metal salt of a phosphate ester compound represented by the following general formula (1).(In the formula, R is a hydrocarbon group having 8 to 35 carbons, OA is an oxyalkylene group having 2 to 4 carbons, n is a number from 1 to 30, being an average number of moles of alkylene oxide added, and m is an integer from 1 to 3)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antiblocking agent and a method for producing resin pellets. [Background technology]

[0002] Amorphous or low-crystalline olefin resins, particularly linear low-density polyethylene and resins copolymerized with ethylene, vinyl acetate, and acrylic esters, are sticky, causing pellets to stick together and form clumps, a phenomenon known as blocking (sticking together). This can make it difficult to remove the pellets from the bag during molding, or can prevent the pellets filled in the hopper of the extruder from being fed stably to the cylinder.

[0003] Various methods have been proposed to reduce the stickiness of the surface of such sticky resin pellets and prevent blocking. For example, a method of coating the surface of rubber pellets with silicone oil (see Patent Document 1) or a method of attaching an inorganic powder such as talc, silica, or calcium carbonate, a lubricant such as a metal salt of a higher fatty acid or a fatty acid amide, or polyethylene powder as an anti-blocking agent to the surface of the easily sticky pellets (see Patent Document 2) is known. Another method is to use an underwater-cut extruder equipped with a pelletizer to extrude a molten resin into water in which silicone oil has been finely dispersed, and pelletize the resin, thereby attaching a liquid to the surface of the pellets (see Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 48-47934 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-105202 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-246854 Summary of the Invention [Problem to be solved by the invention]

[0005] In these methods for preventing blocking of pellets, it is necessary to uniformly disperse and coat as little antiblocking agent as possible on the surface of the olefin resin pellets so as not to deteriorate the performance (e.g., transparency) of the olefin resin or its molded product. However, it is difficult to uniformly and thinly adhere a small amount of antiblocking agent to the resin surface, and a sufficient antiblocking effect cannot be obtained. Furthermore, in the method of coating the pellet surfaces with silicone oil dispersed in cooling water, environmental considerations such as water treatment must be taken into account. An object of the present invention is to provide an anti-blocking agent that can prevent blocking of adhesive resin pellets, particularly that can uniformly and thinly adhere (coat) a small amount of anti-blocking agent to the surface of a resin such as a soft olefin-based resin, and that does not contaminate a resin pellet manufacturing apparatus and is suitable for the production of resin pellets, and to provide a method for producing resin pellets using the same. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the present inventors have found that resin pellets in which blocking is prevented can be obtained by extruding a molten olefin resin from a die nozzle using an extruder, cutting the resin into pellets in cooling water containing a specific phosphate ester compound, and solidifying the pellets with cooling water, thereby completing the present invention.

[0007] That is, the present invention relates to the following [1] to [4]. [1] An antiblocking agent containing a Group 2 metal salt of a phosphate ester compound represented by the following general formula (1): [ka] (In the formula, R is a hydrocarbon group having 8 to 35 carbon atoms, OA is an oxyalkylene group having 2 to 4 carbon atoms, n is a number of 1 to 30 which is the average number of moles of alkylene oxide added, and m is an integer of 1 to 3.) [2] The antiblocking agent according to [1], wherein the Group 2 metal is at least one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). [3] The anti-blocking agent according to [1] or [2], which is used for producing resin pellets. [4] A method for producing resin pellets, comprising a pelletizing step of cutting a resin extruded in a molten state from an extruder while cooling it with cooling water or after cooling it, A method for producing resin pellets, characterized in that a Group 2 metal salt of a phosphoric ester compound represented by the following chemical formula (2) is added to the cooling water: [ka] (In the formula, R, OA, m, and n have the same meanings as above.) [Effects of the Invention]

[0008] The anti-blocking agent of the present invention can prevent blocking of resin pellets having adhesive properties, particularly resin pellets such as soft olefin-based resins, and does not contaminate the resin pellet manufacturing equipment. The method for producing resin pellets of the present invention is more economical than conventional methods for producing pellets with anti-blocking properties because it does not require complicated steps and it is not necessary to separate the step of producing pellets from the step of attaching an anti-blocking agent to the pellets. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of an underwater cut type resin pellet manufacturing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below.

[0011] <Phosphate ester compounds> The phosphate ester compound constituting the antiblocking agent of the present invention is a compound represented by the following general formula (1). [ka] (In the formula, R is a hydrocarbon group having 8 to 35 carbon atoms, OA is an oxyalkylene group having 2 to 4 carbon atoms, n is the average number of moles of alkylene oxide added and is a number from 1 to 30, and m is an integer from 1 to 3.)

[0012] In the general formula (1), R represents a hydrocarbon group having 8 to 35 carbon atoms, and examples thereof include an alkyl group having 8 to 24 carbon atoms, an alkenyl group having 8 to 24 carbon atoms, and an aryl group which may have a substituent.

[0013] Specific examples of alkyl groups having 8 to 24 carbon atoms include n-octyl, n-decyl, dodecyl (lauryl), tridecyl, isotridecyl, tetradecyl (myrstyl), hexadecyl (palmityl), octadecyl (stearyl), eicosyl, docosyl (behenyl), and tetracosyl groups. Specific examples of alkenyl groups having 8 to 24 carbon atoms include octenyl, nonenyl, decenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, eicosenyl, docosenyl, and tetracosenyl groups, which may have a branched or cyclic structure. Examples of the aryl group which may have a substituent include unsubstituted aryl groups such as a phenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a biphenyl group, and a naphthyl group, and the above aryl groups which have a substituent such as a hydrocarbon group having 1 to 24 carbon atoms, an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, and an alkoxy group having 2 to 24 carbon atoms. Among these, from the viewpoint of good adsorption to resins, alkyl or alkenyl groups having 12 to 22 carbon atoms are preferred, and dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl and octadecyl groups are particularly preferred.

[0014] In the general formula (1), OA is an oxyalkylene group having 2 to 4 carbon atoms, specifically an oxyethylene group, a 1,2- or 1,3-oxypropylene group, or a 1,2-, 1,3-, or 1,4-oxybutylene group. Among these, an oxyethylene group and a 1,2-oxypropylene group are preferred, and an oxyethylene group is particularly preferred. n is the average number of moles of alkylene oxide added, and is a number of 1 to 30, but from the viewpoint of dispersibility in water, it is preferably a number of 3 to 20, and more preferably a number of 5 to 10. When n is 2 or more, n OA may be the same or different, and when they are different, it is represented by -(OA) n - may be any of the addition forms of random addition, block addition, and alternating addition. m is an integer of 1 to 3, and preferably 1 or 2.

[0015] The phosphate ester compound used in the present invention can be obtained by a known production method, for example, by reacting a polyalkylene glycol compound represented by the following general formula with a phosphating agent to form a phosphate ester. R-(OA) n -OH (2) (In the formula, R, OA, and n have the same meanings as above.) The phosphorylating agent may be, for example, a known phosphorus compound such as orthophosphoric acid, phosphorus pentoxide (phosphoric anhydride), polyphosphoric acid, phosphorus oxychloride, etc. These may be used alone or in combination of two or more.

[0016] The antiblocking agent of the present invention contains a Group 2 metal salt of the above-mentioned phosphate ester compound. Examples of Group 2 metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0017] Examples of the Group 2 metal salt of the phosphate ester compound include a phosphate monoester represented by the following general formula (3) and a phosphate diester represented by the following general formula (4). [ka] (In the formula, R 1 and R 2 is a hydrocarbon group having 8 to 35 carbon atoms, and OA 1 and OA 2 is an oxyalkylene group having 2 to 4 carbon atoms, n1 and n2 are numbers of 1 to 30 which are the average number of moles of alkylene oxide added, and M is a Group 2 metal.

[0018] The ratio of the phosphoric acid monoester to the phosphoric acid diester is usually 99 / 1 to 1 / 99 by mass, but from the viewpoint of adsorption to resins, a ratio of 90 / 10 to 10 / 90 is preferred, and a ratio of 70 / 30 to 30 / 70 is more preferred. The ratio of the phosphoric acid monoester to the phosphoric acid diester can be determined by measuring the first equivalent acid value, the second equivalent acid value, and the third equivalent acid value by potentiometric titration and calculating from the calculated molecular weight; for example, a method for this calculation is described in JP-B-57-61358.

[0019] <Adhesive resin> The resin constituting the resin pellets produced in the present invention is not particularly limited, but particularly when a surface treatment is performed for the purpose of preventing blocking, a soft resin having adhesive properties, particularly an olefin-based resin, is used. Examples of adhesive soft resins include those whose melting points cannot be measured by a differential scanning calorimeter and resins whose melting points are 80° C. or lower. The anti-blocking agent of the present invention can also be applied to the production of non-sticky resin pellets.

[0020] Examples of olefin-based resins include polyethylene, polypropylene, and copolymers and mixtures thereof. Examples of polyethylene include ethylene homopolymers and copolymers of ethylene with other α-olefins. The α-olefin used as a comonomer is preferably an α-olefin having 3 to 20 carbon atoms. Specific examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, and 4,4-dimethylpentene-1. Specific examples of such ethylene-α-olefin copolymers include ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, and ethylene-4-methyl-pentene-1 copolymers. Among these, ethylene-1-butene copolymers and ethylene-1-hexene copolymers are preferred. Among these, copolymers with a density of 0.935 g / cm are preferred. 3 Low density polyethylene below 0.86 to 0.90 g / cm 3 This method can also be applied to ultra-low density ethylene-α-olefin copolymers, which have high pellet adhesion and are therefore ideal resins for confirming the anti-blocking effect of the present invention. The density of ethylene-α-olefin copolymers is measured (23°C) in accordance with JIS-K6922-2:1997 Appendix (for low-density polyethylene).

[0021] These olefin-based resins such as ethylene-α-olefin copolymers can usually be produced using known Ziegler catalysts, vanadium catalysts, metallocene catalysts, etc. In this case, known production methods include high-pressure ionic polymerization, gas-phase polymerization, solution polymerization, and slurry polymerization.

[0022] The antiblocking agent of the present invention can also be used in the production of resin pellets such as propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and styrene-butadiene rubber.

[0023] <Manufacturing method for resin pellets> Known methods can be used to produce resin pellets. For example, a method can be used in which a molten resin extruded from a die nozzle of an extruder is continuously cooled, solidified, and cut. Specific examples include an underwater cutting method in which a molten resin is extruded from the die of the extruder into cooling water to form a resin strand, which is cooled and solidified and simultaneously cut into pellets with a cutter blade, and a strand cutting method in which the extruded resin is taken up in the form of a strand, solidified by cooling water, and then cut into pellets with a cutter blade.

[0024] The resin pellets are usually cylindrical, spherical, or oval in shape, and usually have a diameter of 1 to 20 mm and a length of 1 to 20 mm.

[0025] Methods for adhering the anti-blocking agent of the present invention to the surfaces of resin pellets include a method in which the anti-blocking agent is added to cooling water during pelletization to adhere to the pellet surfaces, a method in which a solution of the anti-blocking agent is sprayed after pelletization, and a method in which the anti-blocking agent is added to a pellet storage silo and blended.

[0026] When the anti-blocking agent of the present invention is added to cooling water, the concentration of the anti-blocking agent in the cooling water is preferably 100 ppm or more, more preferably 200 ppm or more, from the viewpoint of the effect of preventing blocking of resin pellets. Furthermore, the concentration of the phosphate ester compound in the cooling water is preferably 5000 ppm or less, 3000 ppm or less, or 2000 ppm or less. If the concentration in the cooling water is too high, economic efficiency may decrease and the performance of the resin may also decrease. The location of addition of the anti-blocking agent is not particularly limited. In the case of an underwater cut system, the anti-blocking agent may be added anywhere in the circulating cooling water line in FIG. 1, for example, to the circulating cooling water tank 5. [Example]

[0027] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The antiblocking agents used in the examples and comparative examples were evaluated according to the following methods.

[0028] <Pellet adhesion test> 100 g of sample pellets were placed in a polyethylene cup with an inner diameter of 80 mm, and a load of 13 kPa was evenly applied thereon, followed by leaving the cup to stand in a 40°C atmosphere for one week. The pellets were then removed and evaluated as follows: no pellet blocking, slight blocking, and a large amount of blocking. This test was performed three times and evaluated.

[0029] <Contamination of cooling water> A predetermined amount of anti-blocking agent was added to cooling water adjusted to a temperature of 20°C, and the solubility was confirmed by visual observation. The state in which the agent dissolved in water without any precipitate was evaluated as ○, the state in which the agent dispersed in water but was cloudy was evaluated as △, and the state in which the agent was insoluble in water was evaluated as ×.

[0030] Example 1 Melted linear low-density polyethylene (KJ640T manufactured by Japan Polyethylene Co., Ltd., density 0.880 g / cm 3 , MFR=30 g / 10 min, melting point 58°C) was extruded using a single-screw extruder into cooling water containing calcium salt of a phosphate ester compound (in general formula (1), R: isotridecyl group, A: oxyethylene group, n: 6, monoester:diester=49% by mass:51% by mass) so that the concentration of the calcium salt was 200 ppm relative to the cooling water, and pelletized by the underwater cut method. The surface moisture of the resulting pellets was removed using a centrifuge, and the pellets were dried at 25°C for 12 hours. Then, their blocking resistance was evaluated. The pellets did not stick to each other and did not form lumps.

[0031] Example 2 Pelletization was carried out in the same manner as in Example 1, except that 1000 ppm of a calcium salt of a phosphate ester compound was added to the cooling water. When the blocking resistance of the obtained pellets was evaluated, the pellets did not stick to each other and did not form lumps.

[0032] Examples 3 to 7 Pelletization was carried out in the same manner as in Example 1, except that a phosphate ester compound shown in Table 1 was used as the antiblocking agent. The evaluation results are shown in Table 1.

[0033] Comparative Example 1 Except for not adding an anti-blocking agent to the cooling water, the same procedure was carried out as in Example 1. When the blocking resistance of the obtained pellets was evaluated, it was found that the pellets adhered to each other and formed clumps.

[0034] Comparative Examples 2 to 9 Pelletization was carried out in the same manner as in Example 1, except that the antiblocking agents shown in Table 1 were used. The evaluation results are shown in Table 1.

[0035] [Table 1]

[0036] As shown in Table 1, the anti-blocking agent of the present invention dissolved in cooling water without forming any precipitates, and was able to suppress blocking of resin pellets. [Explanation of symbols]

[0037] 1: Extruder 2: Cutter 3: Underwater hot cutting section 4: Dehydration cyclone 5: Circulating cooling water tank 6: Circulation pump

Claims

1. An anti-blocking agent containing a phosphoric acid monoester represented by the following general formula (3) and a phosphoric acid diester represented by the following general formula (4) in a mass ratio of monoester / diester = 70 / 30 to 30 / 70. 【Chemical 1】 (In the formula, R １ and R ２ is a hydrocarbon group having 8 to 35 carbon atoms, and OA １ and O.A. ２ is an oxyalkylene group having 2 to 4 carbon atoms, n1 and n2 are numbers from 1 to 30 which are the average number of moles of alkylene oxide added, and M is a Group 2 metal.

2. 2. The antiblocking agent according to claim 1, wherein the Group 2 metal is at least one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

3. The anti-blocking agent according to claim 1 or 2, which is used for producing resin pellets.

4. A method for producing resin pellets, comprising a pelletizing step of cutting a resin extruded in a molten state from an extruder while cooling the resin with cooling water or after cooling the resin, A method for producing resin pellets, comprising adding to the cooling water a Group 2 metal salt of a phosphoric acid ester compound represented by the following chemical formula (2): 【Chemistry 2】 (In the formula, R is a hydrocarbon group having 8 to 35 carbon atoms, OA is an oxyalkylene group having 2 to 4 carbon atoms, n is a number from 1 to 30 which is the average number of moles of alkylene oxide added, and m is an integer from 1 to 3.)

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