JPH0214934B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to pellets of ethylene copolymer resins which are substantially prevented from setting and have low tackiness, or pellets of hot melt compositions containing said ethylene copolymer resins. Relatively sticky resin pellets, such as pellets of ethylene-vinyl acetate copolymer with a relatively high vinyl acetate content or hot melt compositions containing this copolymer as a main component, are sticky at room temperature. Not only does it congeal during storage, making it difficult to remove it from the packaging bag or box before use, but it also makes it difficult to measure or transport it to each device during the molding, melting, or mixing process. It also has the disadvantage of poor miscibility, and the range of use of the resin or composition has been severely restricted. Various methods have been proposed to reduce the tackiness of the surface of these tacky resin pellets. For example, a method is known in which pellets that tend to become sticky are coated with inorganic powder such as talc, silica, calcium carbonate, or polyethylene powder as an anti-sticking agent, thereby adhering these powders to pellets that tend to become sticky. However, in the case of ethylene-vinyl acetate copolymer, for example, inorganic materials such as talc and silica are not compatible with the copolymer, so adhering these powders may have an adverse effect on performance in end uses. many. In addition, in this method, in order to substantially prevent the pellets from coagulating, it is necessary to mix the anti-blocking agent powder with the pellets in an amount of several to ten-odd percent, and if such an amount of powder is mixed, the properties of the resin being treated will be impaired. There are some drawbacks. For example, when polyethylene powder is sprinkled on ethylene-vinyl acetate copolymer pellets, the adhesion, strength properties, etc. of the ethylene-vinyl acetate copolymer decrease as the amount of powder adheres increases, and the melting properties also change. Furthermore, this method has the disadvantage that dust is generated during the powder mixing process, which causes a deterioration of the working environment. A method to improve these drawbacks is to reduce the stickiness of the pellets by contacting the polymer pellets with an aqueous slurry of finely divided polyolefin powder and coating the polymer pellets with finely divided polyolefin (U.S. Pat. 3528841) or a dispersion of a low-viscosity ethylene-vinyl acetate interpolymer, specifically a low-viscosity ethylene-vinyl acetate copolymer such as "Elvax" D. A method has been proposed (JP-A-48-32939) in which the stickiness of pellets is reduced by coating the pellets by contacting them with a dispersion.
These methods are excellent methods that eliminate the drawbacks of powder mixing methods. However, these methods are also not satisfactory. That is, when the pellets are treated with a water-soluble slurry of ordinary fine polyolefin powder as in the former method, (1) the adhesion of the fine polyolefin pellets is weak, so the polyolefin is likely to be detached during the drying process. (2) Fine polyolefins are difficult to dissolve in solvents, so when treated pellets are used after being dissolved in a solvent, they become cloudy and precipitate. (3) When applied to hot melt composition pellets, since the compatibility of fine polyolefin with the hot melt composition is poor, phase separation of the polyolefin occurs, which adversely affects adhesion. There are drawbacks such as. In addition, in the latter method, since the melting point of the ethylene-vinyl acetate copolymer used as the coating material is low, the effect of preventing pellets from setting at high temperatures is insufficient. The present inventors have completed the present invention as a result of intensive research to eliminate these drawbacks of the prior art and develop an excellent method for preventing pellet caking. That is, the first invention of the present invention provides ethylene copolymer resin pellets () or pellets of a hot melt composition containing an ethylene copolymer resin ().
surface with an average particle size of 10μ or less and a viscosity average molecular weight
600 to 6000°C and a softening point of 80 to 135°C, the second invention relates to a low-tack resin pellet coated with a low molecular weight polyethylene wax having a softening point of 80 to 135°C. In the pellet manufacturing process, an ethylene copolymer resin or a hot melt composition containing an ethylene copolymer resin, an average particle size of 10 μ or less, a viscosity average molecular weight of 600 to 6000,
Ethylene copolymerization with reduced tackiness, characterized in that the pellets are contacted with an aqueous dispersion of a low molecular weight polyethylene wax having a softening point of 80 to 135°C, and at least a part of the surface of the pellets is coated with the polyethylene wax. The present invention relates to a method for producing resin pellets or hot melt composition pellets containing the copolymer resin. In the present invention, the polyethylene wax used to coat the ethylene copolymer resin pellets or the hot melt composition pellets containing the copolymer resin has an average particle size of 10 μm or less and a viscosity average molecular weight of 10 μm or less.
600 to 6000, preferably 1000 to 4000, and a softening point (ring and ball method) of 80 to 135°C, preferably 100 to 125°C. The viscosity average molecular weight of the polyethylene wax was determined by measuring the intrinsic viscosity [η] of the wax at 135°C in decalin and using the following formula. M ^V =2.51×10 ⁴ [η] ^1.235 The softening point of the wax was measured by the ring and ball method (JIS K2531). The molecular weight of the polyethylene wax used is 600.
Below, the wax itself has a certain degree of stickiness,
Therefore, the anti-caking effect is insufficient, and 6000
In this case, the adhesion of the coated polyethylene wax to the pellets is insufficient, and the solubility of the wax in solvents is also poor, resulting in cloudiness and precipitation when the treated pellets are dissolved in a solvent and used. Furthermore, when applied to a hot melt composition, there are drawbacks such as poor compatibility between the polyethylene wax and the hot melt composition, and phase separation is likely to occur, both of which are undesirable. Also, the softening point of the polyethylene wax used is
Below 80℃, the anti-condensation effect is insufficient, and
If the temperature is higher than 135°C, the adhesion of the polyethylene wax pellets will deteriorate, and as a result, the anti-caking effect will be insufficient, which is not preferable. The average particle size of polyethylene wax is 10μ or less. By using a particle having such a particle size, it is effective even when used in a small amount, is difficult to peel off, and is easily dissolved even when dissolved in a solvent. If the average particle size of the polyethylene wax becomes too large, it is undesirable because it is easily detached from the pellets and its solubility in solvents becomes poor. These polyethylene waxes can be produced by various methods, but specifically, ethylene or ethylene and a small amount of α-olefin are mixed in the presence of hydrogen.
An example is a method of direct polymerization using a Ziegler type catalyst. Furthermore, in the present invention, the ethylene copolymer resin that is subjected to the non-stick treatment is a resinous ethylene copolymer that itself has adhesive properties, such as ethylene-vinyl acetate copolymer, ethylene-vinyl propionate copolymer, etc. Ethylene-α,β-unsaturated carboxylic acid ester copolymers such as ethylene-vinyl ester copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers, etc.; Ethylene-vinyl ester-unsaturated carboxylic acid terpolymer such as vinyl acetate-acrylic acid copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, partially or completely saponified product of ethylene-vinyl acetate copolymer Examples include. Among these, the most preferred ethylene copolymer resin to which the present invention is applied has a vinyl acetate content of 20 to 20.
It is an 85% by weight ethylene-vinyl acetate copolymer. Further, the present invention can also be applied to resin compositions in which various stabilizers, additives, fillers, etc. are blended with ethylene copolymer resin. Further, in the present invention, a hot melt composition containing an ethylene copolymer resin to be detackified is a hot melt composition containing the above-mentioned ethylene copolymer resin and tackifying resin as main components, and optionally including wax, elastomer, oil, etc. Alternatively, it is a composition containing a plasticizer, etc., and is used as an adhesive or a coating agent. The general blending ratio is as follows, for example. Ethylene copolymer resin 20 to 60 parts by weight Tackifying resin 20 to 60 parts by weight Wax, others 0 to 40 parts by weight Tackifying resins include rosin, rosin derivatives, polyterpene resins, terpene-phenolic resins, low molecular weight polystyrene, and low molecular weight Examples include styrene copolymers and petroleum resins. In the present invention, ethylene copolymer resin or hot melt composition pellets thereof have a viscosity average molecular weight of 600.
For coating with polyethylene wax having a softening point of 80 to 6000°C and a softening point of 80 to 135°C, an aqueous dispersion containing the polyethylene wax as the main solid content (hereinafter simply referred to as an aqueous dispersion of polyethylene wax) is used. The polyethylene wax aqueous dispersion used in the present invention can have a solid content concentration of up to about 50% by weight, but since a specific polyethylene wax is used as an anti-blocking agent, the resin pellets may not coagulate. For the purpose of prevention, a sufficient effect can be obtained with a concentration of 0.1% by weight or more, and a dispersion having a solid content concentration of 0.1 to 50% by weight, particularly 0.1 to 20% by weight, is usually preferred. In the aqueous dispersion of polyethylene wax used in the present invention, the polyethylene wax in the dispersion preferably has an average particle size of 10 μm or less. This aqueous dispersion, for example, involves melting the above polyethylene wax, stirring it in water at a temperature of 140 to 300°C and above the melting point of the polyethylene wax in the presence or absence of the dispersion, and then cooling it to room temperature. It can be manufactured by The most preferable polyethylene wax aqueous dispersion that can be used in the present invention from the viewpoint of non-coagulating properties and solvent solubility of the resin pellets after treatment is as follows:
Polyethylene wax (a) with a molecular weight of 300 to 6000 and a softening point of 80 to 140°C, and a carboxyl group-containing polyolefin (b) with an acid value of 30 to 150 [η] 0.04 to 1 and 1 to 50% of the polyethylene wax. This is a dispersion liquid with an average particle size of 10 μm or less obtained by dispersing a composition of the above in water containing a basic substance. The carboxyl group-containing polyolefin used for preparing this dispersion is ethylene, propylene, 1-
Wax consisting of a single or copolymer of 1-olefinic unsaturated hydrocarbons such as butene, polyolefins such as high molecular weight polyethylene and polypropylene, and α,β-unsaturated substances such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. It is modified with carboxylic acid. Basic substances include substances that act as bases in water, such as alkali metals or their oxides, hydroxides, hydrides, alkaline earth metals or their oxides, hydroxides, weak acid salts, and hydrides; metal alkoxides can be used. As a method for preparing this dispersion, for example, the method disclosed in JP-A-52-13539 can be used. When coating ethylene copolymer resin pellets or hot melt composition pellets containing the copolymer resin with polyethylene wax, the copolymer resin or the hot melt composition containing the copolymer resin and an aqueous dispersion of the wax are combined. The contacting can be carried out at any stage of the pellet manufacturing process. For example, a method in which the resin strands are made into pellets and then brought into contact with the aqueous dispersion, a method in which the resin strands immediately before pelletization are brought into contact with the aqueous dispersion and then made into pellets, and a method in which the resin strands are made into pellets and the aqueous dispersion is brought into contact with the aqueous dispersion at the same time as the production of pellets. There are ways to make contact. More specifically, (1) pellets of an ethylene copolymer or a hot melt composition containing the copolymer are immersed in an aqueous dispersion of polyethylene wax, or the pellets are soaked in polyethylene wax while stirring or flowing. A method in which the pellets are brought into contact with an aqueous dispersion of Tux by sprinkling with the aqueous dispersion, and then dried. (2) A method in which a strand of an ethylene copolymer or a hot melt composition containing the copolymer discharged from a die of an extruder is passed through an aqueous polyethylene wax dispersion and then cut into pellets. (3) A method in which an ethylene copolymer or a melt of a hot melt composition containing the copolymer discharged from a die of an extruder is hot-cutted while being discharged into an aqueous polyethylene dispersion. can be exemplified. Regardless of which method is adopted, the contact time between the ethylene copolymer resin or the hot melt composition containing the copolymer resin and the aqueous dispersion of polyethylene wax is extremely short, and the pellet surface is coated with the aqueous dispersion. The purpose is achieved by getting wet. The temperature during pellet coating is not particularly limited as long as the dispersion is liquid, and is usually 0 to 140°C.
℃, especially 10 to 80℃ is preferred. In the present invention, a surfactant may be added to the aqueous dispersion for the purpose of improving wetting of the dispersion to the pellet surface. The amount of polyethylene wax solids attached to the pellet surface varies depending on the type of pellet to be treated, but it is usually
It is sufficient to deposit 0.020 to 0.30% by weight,
Of course, there is no problem in attaching more than this. In the present invention, a specific polyethylene wax is used as an anti-blocking agent in the form of an aqueous dispersion, so the amount of coating and adhesion is smaller than that of conventional anti-blocking agents, for example, about 0.02% by weight of the pellet. However, there are advantages such as sufficient prevention of aggregation and good compatibility of the polyethylene wax with the ethylene copolymer, so that the resin performance of the obtained pellets is not impaired. Furthermore, since this polyethylene wax is used as an aqueous dispersion, there is no powder scattering, which occurs with conventional powder sprinkling methods, resulting in a clean work environment and the production of resin pellets with reduced stickiness. In this case, by applying an underwater cutting process, that is, a process in which the melted resin to be detackified is cut while being brought into contact with an aqueous dispersion, pellets that are difficult to coagulate can be produced in one step. . Next, the present invention will be explained in more detail with reference to Examples. The coagulation properties, solubility and compatibility of the pellets described in the Examples below were tested by the following methods. (1) Non-agglomeration 1 kg of resin pellets after non-adhesive treatment was placed in a polyethylene bag, heat-sealed, left in a constant temperature bath at 40℃ for 24 hours, opened, and the degree of coagulation of the pellets was judged according to the following criteria. did. A: There was no condensation at all, and it was discharged from the bag in a flowing manner. B: The pellets are a little stuck together, but they can be crushed relatively easily by hand and almost fall into pieces. C: The pellets are sticking together pretty strongly, but they can be broken into small chunks. D: Strongly stuck together and difficult to break. (2) Solvent solubility 20 g of the resin pellets after the non-stick treatment were dissolved in 80 g of toluene, and after being left at 0° C. for 24 hours, the solution was evaluated based on liquid clarity, phase separation, or presence or absence of precipitates. A: Neither turbidity nor precipitate was observed at all. B: Slight turbidity is observed, but there is no phase separation. C: Considerable turbidity and some sediment are observed. D: Significant precipitation is observed. (3) Compatibility The hot melt composition pellets after the non-adhesive treatment were melted by heating at 180°C, and the compatibility was evaluated based on the transparency and turbidity of the solution. A: It is completely transparent with no turbidity. B: Slightly cloudy. C: Considerably cloudy. D: Completely milky white. Example 1 Acetic acid was added to 2 kg of an aqueous dispersion with an average particle size of 5 μm and a solid content concentration of 1.5% by weight, in which a low molecular weight polyethylene wax with a molecular weight (viscosity average molecular weight) of 2000 and a softening point (ring and ball method) of 120°C was dispersed in water. 1 kg of ethylene-vinyl acetate copolymer resin pellets with a vinyl content of 40%
After soaking, the pellets were passed through a wire mesh and dried. The amount of solid content deposited was 0.075% by weight as determined from pellet weight measurements before and after drying. The pellets thus obtained had a non-caking property of A. Comparative example 1 Molecular weight (viscosity average molecular weight) 16000, softening point 130℃
Solid content concentration of polyethylene dispersed in water
Pellets of ethylene-vinyl acetate copolymer resin coated with polyethylene were obtained in the same manner as in Example 1 except that a 1.5% by weight aqueous dispersion was used. However, the amount of solid content attached to this pellet is
0.023% by weight, and the non-caking property of the pellets was C. Example 2 A low molecular weight polyethylene wax with a molecular weight of 4000 and a softening point of 115°C was dispersed in water with an average particle size of 5μ,
After immersing 10 kg of ethylene-vinyl acetate copolymer resin pellets with a vinyl acetate content of 45% in an aqueous dispersion with a solid content concentration of 3% by weight, the pellets were filtered through a wire mesh, and the drained pellets were dried with hot air. The amount of solid content adhering to the pellets thus obtained was 0.32%. The first priority is the non-caking property and solvent solubility of pellets.
Shown in the table. Comparative Example 2 Polyethylene or paraffin with the molecular weight and softening point shown in Table 1 was dispersed in water with a solid content concentration of 8.
Ethylene-vinyl acetate copolymer resin pellets were treated in the same manner as in Example 2 except that a % by weight aqueous dispersion was used. The amount of solid content, non-caking property, and solvent solubility of the pellets obtained in this way were evaluated as follows.
Shown in the table. Example 3 A low molecular weight polyethylene wax with a molecular weight of 4000 and a softening point of 115°C was dispersed in water with an average particle size of 5μ,
1.5 kg of ethylene-vinyl acetate copolymer in an aqueous dispersion with a solid content concentration of 10% by weight (trade name: Evaflex)
250 manufactured by Mitsui Polychemical Co., Ltd.] 60 parts by weight, tackifier resin [trade name Alcon M-100 manufactured by Arakawa Chemical Co., Ltd.] 40
After immersing 1 kg of pellets of a hot-melt composition containing parts by weight as main ingredients for 30 seconds, the pellets were passed through a wire mesh and dried with hot air. The amount of solid content deposited on the pellets thus obtained was 0.38% by weight. The results of the pellet non-aggregation and compatibility tests are shown in Table 2. Comparative Example 3 Polyethylene or paraffin with the molecular weight and softening point shown in Table 1 was dispersed in water at a solid concentration of 10.
Ethylene-vinyl acetate copolymer resin pellets were treated in the same manner as in Example 3, except that an aqueous dispersion of 5% was used. Table 2 shows the test results for solid content adhesion, non-caking property and compatibility of the pellets thus obtained.

【table】

[Table] Example 4 Acrylic acid grafted polyethylene wax ([η] = 0.20, acid value 100, softening point
128°C) were melt-mixed at 200°C. Separately, put 240ml of water and 6g of sodium hydroxide in a pressure-resistant homomixer with an internal volume of 10, and heat it to 180℃.
While stirring at 5000 rpm, the above-mentioned composition of molten acrylic acid grafted polyethylene wax and polyethylene was supplied by a gear pump for 1 hour, and after further stirring for 30 minutes, it was cooled to room temperature.
An aqueous dispersion containing finely divided polyethylene wax having a spherical shape and a number average particle size of 1 μm or less was obtained.
Water was added to this dispersion to adjust the solid content concentration to 7%. Approximately 1 kg of ethylene-vinyl acetate copolymer resin pellets containing 45% vinyl acetate was added to 2 kg of the aqueous dispersion of polyethylene wax thus prepared.
After soaking for 15 seconds, it was dried with hot air. The pellets thus obtained were both A in non-agglomeration and solvent solubility.

Claims (1)

[Scope of Claims] 1. The surface of the ethylene copolymer resin pellets () or the hot melt composition pellets () containing the ethylene copolymer resin has an average particle diameter of 10 μm or less, a viscosity average molecular weight of 600 to 6000, and a softening point of 80. Low-stick resin pellets coated with low molecular weight polyethylene wax at a temperature of 135°C to 135°C. 2 Claim 1 in which the ethylene copolymer resin is an ethylene-vinyl ester copolymer or an ethylene-α,β-unsaturated carboxylic acid ester copolymer
Resin pellets as described. 3. The resin pellet according to claim 1, wherein the ethylene copolymer resin is an ethylene-vinyl acetate copolymer. 4. The pellets according to claim 1, wherein the ethylene copolymer resin is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 85% by weight. 5. In the process of manufacturing ethylene copolymer resin pellets or pellets of a hot melt composition containing an ethylene copolymer resin, the ethylene copolymer resin or a hot melt composition containing an ethylene copolymer resin and an ethylene copolymer resin having an average particle size of 10 μm or less and an average viscosity of molecular weight 600
6,000° C. and a softening point of 80 to 135° C., and at least a part of the surface of the pellet is coated with the polyethylene wax. A method for producing ethylene copolymer resin pellets or hot melt composition pellets containing the copolymer resin. 6. Claim 5, wherein the coating is carried out by contacting ethylene copolymer resin pellets or pellets of a hot melt composition containing ethylene copolymer resin with an aqueous dispersion whose main solid content is the low molecular weight polyethylene wax. the method of. 7. After bringing the above coating into contact with a strand of an ethylene copolymer resin or a hot melt composition containing the copolymer resin discharged from an extrusion die with an aqueous dispersion whose main solid content is the low molecular weight polyethylene wax, The method according to claim 5, which is carried out by strand cutting. 8. The above-mentioned coating is applied by contacting a melt of an ethylene copolymer resin or a hot melt composition containing the copolymer resin discharged from an extrusion die with an aqueous dispersion whose main solid content is the above-mentioned low molecular weight polyethylene wax. The method according to claim 5, which is carried out by hot cutting. 9 Claim 5 in which the ethylene copolymer resin is an ethylene-vinyl ester copolymer or an ethylene-α,β-unsaturated carboxylic acid ester copolymer
9. The method according to any one of 8. 10. The method according to any one of claims 5 to 8, wherein the ethylene copolymer resin is an ethylene-vinyl acetate copolymer. 11 Ethylene copolymer resin has a vinyl acetate content of 20~
9. A method according to any one of claims 5 to 8, wherein the ethylene-vinyl acetate copolymer is 85% by weight. 12 The aqueous dispersion of low molecular weight polyethylene wax is composed of 50 to 99 parts by weight of polyethylene wax having a viscosity average molecular weight of 600 to 6000 and a softening point of 80 to 135°C and 1 to 50 parts by weight of a carboxyl group-containing polyolefin having an acid value of 30 to 150. The method according to any one of claims 5 to 11, which is a dispersion liquid having a solid content of the composition. 13. The method according to any one of claims 5 to 12, wherein the solid content concentration of the low molecular weight polyethylene wax in the aqueous dispersion is 0.1 to 50% by weight.