JP2001294669A - Method for producing thermoplastic resin pellet and thermoplastic resin pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing thermoplastic resin pellets, by which the uniform coating films of a lubricant are simply and efficiently formed on the surfaces of the thermoplastic resin pellets to improve the moldability of the pellets. SOLUTION: This method for producing the thermoplastic resin pellets comprises adding a lubricant and a spreader to the thermoplastic resin pellets from the outside and is characterized as follows; (A) adding 0.005 to 0.5 pt.wt. of a spreader to 100 pts.wt. of the thermoplastic resin pellets, stirring the mixture for a time sufficient for homogeneously mixing the pellets with the spreader, adding 0.01 to 1.0 pt.wt. of a lubricant to the homogeneous mixture, and then stirring the mixture to form the coating films of the lubricant on the surfaces of the pellets; (B) using the lubricant and the spreader in such a combination as exhibiting a pasty state, when the lubricant and the spreader are mixed in a weight ratio of approximately 1:1 at a temperature used in this invention; and (C) performing the mixing agitation of the spreader and the lubricant with the pellets at a temperature which is higher than the melting point of the spreader but lower than the boiling point of the spreader and lower than the melting point of the lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin pellet having excellent moldability and a method for producing the same. More specifically, the present invention relates to a method for forming a uniform film of a lubricant on the surface of a thermoplastic resin pellet.

[0002]

2. Description of the Related Art Thermoplastic resins such as polyamides are used in large quantities in resin parts for automotive and industrial applications by injection molding and extrusion molding. In this case, particularly in injection molding, a high cycle is required in order to increase productivity, and in order to improve plasticity and mold releasability, a lubricant is usually attached to the surface of the thermoplastic resin pellet. Is being done.

As examples of lubricants, metal salts of higher fatty acids such as aluminum salts of stearic acid are frequently used. By adding these lubricants, the plasticizability and mold releasability in the injection molding of the thermoplastic resin certainly improve, but since these higher fatty acid metal salts are usually powders at room temperature, they are simply dusted on pellets. If the powder is simply adhered, the powder is likely to be detached from the pellet surface, causing unevenness in the adhered state, causing variations in the plasticization time and releasability, and the detached powder being scattered, causing the pellet production process and There is a problem that the working environment in the molding process is deteriorated.

Various methods have been tried for this improvement. When the pellets are heated to a temperature equal to or higher than the melting point of the lubricant to be attached to the pellets and then dusted with the powder of the lubricant, the lubricant can be melted to form a uniform lubricant film on the pellet surface. In addition, the thermoplastic resin pellets exposed to a high temperature may be thermally deteriorated and colored.

Japanese Patent Publication No. Hei 8-500549 discloses a technique in which a resin pellet and a lubricant of a higher fatty acid metal salt collide at a high speed in a container, and the kinetic energy is used to form a uniform film of the lubricant on the pellet surface. Is disclosed. But,
To do this on a commercial scale requires complex equipment that requires a lot of energy.

Japanese Patent Application Laid-Open No. 4-65464 discloses that a fatty acid carboxylic acid derivative wax is used to spread a higher fatty acid metal salt on resin pellets.
It is exemplified that a uniform film can be formed on the pellet surface by relatively gentle heating of about ° C. But,
Since this wax is solid at normal temperature, it is necessary to heat the wax to spread the lubricant evenly.If the amount of the wax is large, the melt viscosity of the thermoplastic resin such as polyamide is reduced, and the plasticization property is reduced. Conversely, it is easy to worsen.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a production method for forming a uniform film of a lubricant easily and efficiently on the surface of a thermoplastic resin pellet.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a specific combination of a lubricant and a spreading agent is mixed with a thermoplastic resin pellet by a specific method. As a result, it has been found that a lubricant film can be efficiently formed on the pellet surface with simple equipment, and the present invention has been accomplished. In detail, to the thermoplastic resin pellets, first add a specific liquid spreading agent, cover the pellet surface with a liquid film of the spreading agent, and then add a specific lubricant at a temperature below its melting point. When the mixture is stirred and mixed, the lubricant dissolves in the spreading agent and turns into a paste to form a uniform film on the pellet surface.

That is, the present invention is as follows. (1) A method for producing thermoplastic resin pellets, which is characterized by the following when externally adding a lubricant and a spreading agent to thermoplastic resin pellets. (A) Thermoplastic resin pellet 100
First, 0.005 to 0.5 parts by weight of a spreading agent is added to parts by weight, and stirring is performed for a time sufficient for the spreading agent to be uniformly mixed with the pellets. Add 1.0 part by weight, stir and mix to form a lubricant film on the pellet surface. (B) When the lubricant and the spreading agent are mixed at a main use temperature at a weight ratio of about 1: 1, the combination of the lubricant and the spreading agent that shows a paste state is used. (C) Mixing and stirring the pellets with the spreading agent and the lubricant at a temperature not lower than the melting point of the spreading agent and not higher than the boiling point and not higher than the melting point of the lubricant.

(2) The method for producing thermoplastic resin pellets according to (1), wherein the thermoplastic resin is polyamide.

(3) The method for producing thermoplastic resin pellets according to (1) or (2), wherein the lubricant is a metal salt of a higher fatty acid having 9 or more carbon atoms.

(4) The method for producing thermoplastic resin pellets according to any one of (1) to (3), wherein the spreading agent is a synthetic lubricating oil having HLB> 10 and a nonionic surfactant.

(5) The method for producing thermoplastic resin pellets according to any one of (1) to (4), wherein the mixing and stirring of the thermoplastic resin pellets with the spreading agent and the lubricant are performed by a batch type mixing device. .

(6) The method for producing thermoplastic resin pellets according to any one of (1) to (4), wherein the mixing and stirring of the thermoplastic resin pellets with the spreading agent and the lubricant are performed by a continuous mixing apparatus. .

(7) A thermoplastic resin pellet produced by the method according to any one of (1) to (6).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in detail. Known thermoplastic resins can be used as the thermoplastic resin of the present invention. Examples include polyethylene, polypropylene, polystyrene, polyamide, polyester, polyacetal, and copolymers or blends thereof. Preferably, there is a polyamide, for example, nylon 66, nylon 610, nylon 612, nylon 46, etc. obtained by polycondensation of diamine and dicarboxylic acid, and nylon 6, nylon 12, etc. obtained by ring-opening polymerization of lactam, Nylon 6 is used as a polyamide copolymer.
6/6, nylon 66/610, nylon 66/61
2. Nylon 66 / 6T (T is terephthalic acid component), Nylon 66 / 6I (I is isophthalic acid component) and the like. Polyamide resins composed of blends of these are nylon 66 / nylon 6, nylon 66 / nylon. 612 and the like. As these thermoplastic resin pellets including polyamide, those obtained by polymerization and production by a known method can be used.

The lubricant used in the present invention has a function of improving the moldability such as plasticity and mold release properties by adding to the thermoplastic resin pellets. Examples thereof include paraffin wax and polyolefin wax. Aliphatic fatty acids such as stearic acid and oleic acid, higher fatty alcohols such as stearyl alcohol, higher fatty acid amides such as stearamide, erucamide, ethylenebisstearic acid amide, aluminum stearate and montan Higher fatty acid metal salts such as calcium acid, stearyl stearate, higher fatty acid esters such as montan wax and the like can be used. Preferably, lauric acid,
Sodium, lithium, calcium, magnesium, zinc, and aluminum salts of higher fatty acids having 9 or more carbon atoms such as myristic acid, palmitic acid, stearic acid, behenic acid, montanic acid, melicic acid, oleic acid, and erucic acid. Metal salts such as calcium montanate, sodium montanate, aluminum stearate, calcium stearate, and the like are more preferably used. These lubricants may be used alone or in combination of two or more.

The addition amount of these lubricants is preferably 0.01 to 1.0 part by weight based on 100 parts by weight of the polyamide resin. If the amount is less than 0.01 part by weight, the effect of improving the plasticization property and the releasability is small. If the amount exceeds 1.0 part by weight, the viscosity of the molded article is reduced or silver is generated due to excessive lubricant. Is more likely to occur.

The spreading agent used in the present invention functions to assist the adhesion of the lubricant to the thermoplastic resin pellets. Examples thereof include animal oils such as tallow, whale oil, vegetable oils such as rapeseed oil and soybean oil. Petroleum-based lubricating oils such as oil, spindle oil, engine oil, etc., synthetic lubricating oils such as dimethyl silicone, pentaerythritol ester, poly (α-olefin), polyethylene glycol, polypropylene glycol, polyphenyl ether, and ionicity such as alkylbenzene sulfonate Surfactants, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, high-grade alcohol Fatty acid esters such as capric acid and oleic acid; aliphatic alcohols such as decanol; polyhydric alcohols such as 1,5 pentanediol and glycerin; fatty acid amides such as linoleic acid amide; Fatty acid esters such as stearate can be used, and are organic compounds which become liquid under the use temperature conditions of the present invention. More preferably, HLB (h
hydrophile-lipophile balan
Those having ce) of 10 or more are used. Among them, polyethylene glycol and polyoxyethylene sorbitan fatty acid ester are preferably used. The HLB referred to here is a numerical value representing the balance between a hydrophilic group and a hydrophobic group in a compound (edited by the Chemical Society of Japan, “Chemical Handbook (Applied Chemistry)”, Showa 6)
1st year ”, page 1210, Maruzen). These spreading agents may be used alone or in combination of two or more.

An appropriate amount of the spreading agent is 0.005 to 0.5 parts by weight based on 100 parts by weight of the thermoplastic resin pellets. If the amount is less than 0.005 parts by weight, the ability to dissolve the lubricant is insufficient, the film formation of the lubricant is insufficient, and the lubricant tends to fall off and scatter. If it exceeds 0.5 parts by weight,
The pellets are blocked by the excess liquid spreading agent, and the plasticization is rather deteriorated, and silver is easily generated in the molded product.

As the combination of the lubricant and the spreading agent used in the present invention, those which show a paste when they are mixed at about 1: 1 at the operating temperature to be added to the pellets are used. The expression "paste state" means that when a solid lubricant and a liquid spreader are mixed, the whole or a part of the lubricant dissolves in the spreader to form a viscous mixture. In the case of a combination in which the lubricant and the spreading agent are not separated from each other in a paste form, the powder of the lubricant remains simply adhered to the pellet surface, and the falling off of the lubricant is not improved.
The use of a paste-like combination makes it possible for the first time to form a lubricant film on the pellet surface.

A known mixing and stirring device can be used for mixing the thermoplastic resin pellets with the surfactant and the lubricant. For example, a batch type mixing device such as a tumbler or a Henschel mixer, or a continuous type mixing device such as a drum blender can be used. As a method for heating the pellets, a method in which the mixing apparatus is a jacket type and the jacket is heated with steam or the like to transfer the heat to the pellets is simple and general, but is not limited thereto.

In the present invention, first, a spreading agent is added to and mixed with a thermoplastic resin pellet at a temperature not lower than its melting point and not higher than the boiling point to form a liquid film of the spreading agent on the surface of the pellet. For this purpose, mixing and stirring are performed for a time sufficient for the liquid spreading agent to be uniformly mixed with the pellets. If the mixing temperature is lower than the melting point of the spreading agent, a liquid film cannot be formed. Even above the boiling point, a liquid film cannot be formed.

Next, a lubricant is added and mixed, and the individual lubricant is dissolved in the liquid film layer of the spreading agent on the pellet surface to form a paste-like film. It is preferable to slightly heat the pellet when mixing the lubricant, since the paste is easily formed.
However, in this heating, it is necessary to keep the temperature of the pellets below the melting point of the lubricant. When heated above the melting point of the lubricant, the lubricant melts and sticks the lubricant and pellets to the inner wall of the mixing device. Adding and mixing a spreading agent to the pellets,
The addition and mixing of the lubricant may be carried out in the same mixing device, or may be carried out continuously in separate devices.

If the lubricant is added first and the spreading agent is added later, the formation of a uniform film of the lubricant is hindered, and the lubricant film of the pellets becomes uneven. Therefore, it is necessary to add the lubricant after adding the spreading agent to the pellets first.

The thermoplastic resin pellets of the present invention may contain, if necessary, a polymerization catalyst, a heat stabilizer, a lubricant, a filler such as talc, a reinforcing material such as glass fiber, and a coloring agent. Can be. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The evaluation method is described below.

(1) Paste-formability by mixing lubricant and spreader: A lubricant and a spreader are put into a beaker at a weight ratio of about 1: 1.
The mixture was heated to a temperature at which it was mixed with the pellets, stirred with a glass rod, and the appearance was observed.

(2) Film forming property of lubricant on pellet surface When the pellets were discharged from the mixing device, it was observed whether or not the lubricant powder was scattered. The surface state of the obtained pellet was separately observed with an optical microscope. In the case where the lubricant film was formed on the pellet surface, no powder scattering of the lubricant was observed at the time of dispensing. On the other hand, if the lubricant powder simply adheres to the pellet surface,
Many powder scatters occurred at the time of dispensing.

(3) Sticking property to the inner wall of the pellet mixing apparatus After discharging the pellets, it was observed whether or not the lubricant and the pellet remained fixed on the inner wall of the mixing apparatus.

(4) Plasticization The plasticization was carried out under the following conditions, and the time for the screw to recede was measured and defined as the plasticization time. The average value of the plasticizing time of 50 shots was determined, and the difference between the maximum value and the minimum value was defined as a variation.

Molding machine: PS-40E (manufactured by Nissei Plastic Industry Co., Ltd.) Mold: ASTM-Type I Cylinder temperature: 280 ° C. Mold temperature: 80 ° C. Screw rotation speed: 150 rpm Injection time: 15 seconds Cooling time: 15 seconds

[0032]

Example 1 Nylon 66 (Leona 1300, trade name of Asahi Kasei Kogyo Co., Ltd.) as a thermoplastic resin, calcium montanate (melting point: 122 ° C.) as a lubricant, polyoxyethylene sorbitan monolaurate (Marubishi oil) as a spreading agent Chemical Co., Ltd., trade name: Balu 7220, melting point: 5 ° C. or less, boiling point: 200 ° C. or more / abbreviated as spreader S1).

When the above lubricant and spreading agent were put in a beaker and mixed, a paste was shown. 100 as it is
When heated to ° C., it was paste-like in this temperature range. 100 parts by weight of nylon 66 resin pellets are put into a batch-type Henschel mixer, and the spreading agent S1 is further added.
Was added at room temperature. Next, the pellets and the spreading agent were stirred and mixed while heating the steam of 1.0 kg / cm ² through the jacket of the Henschel mixer. After about 10 minutes, the pellet temperature reached 70 ° C. Thereafter, 0.10 part of calcium montanate was added, and stirring was further continued for 10 minutes, and then heating was stopped. At this time, the pellet temperature was 90 ° C. Cooling was performed by flowing cooling water through the jacket portion, and stirring was stopped when the pellet temperature dropped to 60 ° C. or lower, and the pellets were discharged.

At the time of discharging the pellets, there was no scattering of the lubricant powder, and no adhesion of the lubricant and the pellets was observed on the inner wall of the Henschel mixer after the discharging. Table 1 shows the results of plasticizing evaluation of the obtained pellets.

[0035]

Example 2 In Example 1, an experiment was conducted at room temperature without heating, using a continuous two-stage drum blender as a mixing device. The types and addition ratios of the thermoplastic resin, the spreading agent, and the lubricant were the same as in Example 1. The liquid of the spreading agent S1 was continuously injected into the nylon 66 resin pellets by a predetermined amount by a pump using a first-stage drum blender. The average residence time in the first stage is about 5 minutes and the pellets are subsequently led to a second stage drum blender. In the second-stage drum blender, calcium montanate powder was continuously added as a lubricant with a small feeder, and the mixture was stirred for an average residence time of about 5 minutes. The pellet temperature at the time of discharging the pellet was 30 ° C. Dispersibility of lubricant when dispensing pellets,
Table 1 shows the adhesion of the lubricant and the pellet to the inner wall of the drum blender, and the results of the evaluation of plasticization.

[0036]

Example 3 An experiment was conducted in the same manner as in Example 1 except that monoaluminum stearate (melting point: 150 ° C.) was used as a lubricant. When monoaluminum stearate and the spreading agent S1 were mixed, a paste was formed at room temperature. When it was directly heated to 100 ° C., it was paste-like in this temperature range. Table 1 shows the scattering properties of the lubricant when the pellets were dispensed, the adhesion of the lubricant and the pellets to the inner wall of the Henschel mixer, and the results of the plasticization evaluation.

[0037]

Example 4 In Example 2, monoaluminum stearate was used as a lubricant, and polyethylene glycol (PEG # 400, trade name of NOF Corporation, melting point: about 8 ° C., boiling point: 200 ° C. or more) was used as a spreading agent. An experiment was performed similarly. When the above lubricant and surfactant were mixed, a paste was formed at room temperature. Table 1 shows the scattering properties of the lubricant when the pellets were dispensed, the adhesion of the lubricant and the pellets to the inner wall of the drum blender, and the results of the plasticization evaluation.

[0038]

[Comparative Example 1] In Example 1, without using a spreading agent,
Experiments were performed with similar heating and time settings. Table 1 shows the scattering properties of the lubricant when the pellets were dispensed, the adhesion of the lubricant and the pellets to the inner wall of the Henschel mixer, and the results of the plasticization evaluation.

[0039]

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that steam of 5.0 kg / cm ² was passed through the jacket of the Henschel mixer. At the time of adding calcium lubricant montanate, the temperature of the pellet is 130 ° C.,
After 10 minutes of mixing and stirring, the pellet temperature was 140
° C. Dispersibility of lubricant when dispensing pellets,
Table 1 shows the adhesion of the lubricant and the pellet to the inner wall of the Henschel mixer, and the results of the evaluation of plasticization.

[0040]

Comparative Example 3 The same experiment as in Example 1 was carried out except that calcium montanate was used as a lubricant and polyethylene glycol was used as a spreading agent. When the above lubricant and the spreading agent were mixed, the mixture did not become a paste, but the powdered calcium montanate and the liquid polyethylene glycol were clearly separated. The same was true even when heated to 100 ° C. Table 1 shows the scattering properties of the lubricant when the pellets were dispensed, the adhesion of the lubricant and the pellets to the inner wall of the Henschel mixer, and the results of the plasticization evaluation.

[0041]

[Table 1]

The abbreviations in Table 1 are as follows. PA66: Nylon 66 resin pellet S1: Polyoxyethylene sorbitan monolaurate

[0043]

According to the present invention, the following useful effects were obtained only when the specific combination of the spreading agent and the lubricant shown in the present invention was used and the specific conditions were set. 1) A lubricant film can be formed on the pellets, and there is no scattering of powders when dispensing the pellets and during subsequent handling.
A good working environment is maintained. 2) There is no adhesion of lubricant and pellets inside the mixing device, and continuous production is possible. 3) Since the lubricant does not fall off due to the formation of a uniform lubricant film on the pellets, it exhibits stable plasticization with little variation during injection molding and enables high cycle molding.

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Claims (7)

[Claims] 1. A method for producing thermoplastic resin pellets, which comprises adding a lubricant and a spreading agent to a thermoplastic resin pellet externally. (A) First, 0.005 to 0.5 parts by weight of a spreading agent is added to 100 parts by weight of the thermoplastic resin pellets, and the mixture is stirred for a time sufficient to uniformly mix the spreading agent with the pellets.
Thereafter, 0.01 to 1.0 parts by weight of a lubricant is added and mixed by stirring to form a lubricant film on the pellet surface. (B) When the lubricant and the spreading agent are mixed at a main use temperature at a weight ratio of about 1: 1, the combination of the lubricant and the spreading agent that shows a paste state is used. (C) Mixing and stirring the pellets with the spreading agent and the lubricant at a temperature not lower than the melting point of the spreading agent and not higher than the boiling point and not higher than the melting point of the lubricant. 2. The method for producing thermoplastic resin pellets according to claim 1, wherein the thermoplastic resin is polyamide. 3. The method for producing thermoplastic resin pellets according to claim 1, wherein the lubricant is a metal salt of a higher fatty acid having 9 or more carbon atoms. 4. The method according to claim 1, wherein the spreading agent is a synthetic lubricating oil having an HLB> 10 and a nonionic surfactant.
4. The method for producing a thermoplastic resin pellet according to any one of items 1 to 3. 5. The method for producing thermoplastic resin pellets according to claim 1, wherein the mixing and stirring of the thermoplastic resin pellets with the spreading agent and the lubricant are performed by a batch type mixing device. . 6. The method for producing thermoplastic resin pellets according to claim 1, wherein the mixing and stirring of the thermoplastic resin pellets, the spreading agent, and the lubricant are performed by a continuous mixing device. . 7. A thermoplastic resin pellet produced by the method according to claim 1.