JPH10212359A - Polyolefin mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mixture containing masterbatch pellets highly filled with an inorganic filler and a diluting pellets, which is made proof against the segregation and therefore have a uniform composition during molding by previously adding an antistatic agent to only the diluting pellets. SOLUTION: This mixture is obtained by mixing polyolefin masterbatch pellets prepared by filling a polyolefin with 50-90wt.% inorganic filler with diluting polyolefin pellets and previously adding 0.01-2phr antistatic agent to only the diluting polyolefin pellets. Usually, the ratio of the mean particle diameter of the masterbatch pellets to that of the diluting pellets are desirably 0.7-1.3. Usually, the mixing ratio is preferably such that the final concentration of the inorganic filler is about 5-50wt.%. The antistatic agent is added to the diluting pellets by a method such as the one comprising dispersing the agent in the polyolefin and pelletizing the mixture or the one comprising coating pellets of the polyolefin with the agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to novel polyolefin mixtures useful as molding materials. For more information,
This is a polyolefin mixture that can prevent segregation of a mixture of a polyolefin masterbatch pellet highly filled with an inorganic filler and a polyolefin pellet for dilution, and can homogenize the composition during molding.

[0002]

2. Description of the Related Art As is well known, polyolefins such as polypropylene resins are widely used for various purposes as general-purpose resins which are balanced in "physical properties", "moldability" and "economical efficiency".

[0003] In particular, when the polyolefin is filled with an inorganic filler such as talc, calcium carbonate, glass fiber or the like, it has advantages such as thermal and mechanical properties such as heat resistance, rigidity and creep resistance. Used mainly in large quantities.

In general, in a method for producing a polyolefin containing an inorganic filler, both are mixed at a predetermined ratio at the time of molding, and then granulated into pellets and then supplied to a molding machine. It has the disadvantage that it is newly generated and the product cost increases.

[0005] As a solution to the above-mentioned drawback, a polyolefin pellet (hereinafter also referred to as a masterbatch pellet), which has been prepared in advance and is filled with an inorganic filler at a concentration higher than that usually used for polyolefin, is prepared. Of polyolefin pellets (hereinafter also referred to as pellets for dilution) substantially containing no, are directly mixed by an injection molding machine, an extrusion molding machine, or the like.

[0006]

According to the above method, the cost can be greatly reduced by increasing the dilution ratio of the diluted pellets. Or during transport to the molding machine, furthermore, in the hopper on the molding machine, a phenomenon in which the masterbatch pellets and the diluted pellets are separated, a so-called segregation phenomenon occurs, and the inorganic filler concentration in the molded product deviates from the specified amount, physical properties, There is a disadvantage that the weight, product dimensions, and the like vary.

This segregation phenomenon is caused by the influence of friction between the pellets and the contact between the pellets and each device in the process of mixing the master batch pellets and the pellets for dilution or transporting the mixture by an air transport device or the like. It is considered that the material is charged by the generation of static electricity and adheres to a wall or the like in the system.

Further, it is presumed that the difference in specific gravity between the masterbatch pellet and the diluted pellet causes a difference in the amount of adhesion due to static electricity, resulting in an increase in quality variation.

As a general means for solving the problem caused by the static electricity, there has been proposed a method of adding an antistatic agent to the masterbatch pellet and the pellet for dilution and then mixing them.

For example, Japanese Patent Publication No. 4-56052 discloses a polyolefin masterbatch pellet obtained by adding one or more additives to a polyolefin at a high concentration and granulating the polyolefin masterbatch pellet with the same chemical type as the masterbatch pellet. A method for mixing polyolefin pellets in which the concentration of the additive in the mixture is suitable for molding by mixing with polyolefin pellets containing no polyolefin, wherein the pellet mixture being mixed has an antistatic property of 0.005 to 2 phr. A method for preventing classification of a polyolefin masterbatch pellet mixture to be added and mixed is shown.

However, the total concentration of the exemplified additives of the masterbatch of interest in the above process is at most 70 phr (about 41% by weight) and in the examples also 60 phr (37.5% by weight).

[0012] The present invention is characterized in that an antistatic agent is added afterwards to the master batch to be treated.

However, when an inorganic filler is used as the above additive and the concentration of the inorganic filler in the masterbatch further increases from the above range, the antistatic agent is added to the masterbatch pellet and the diluted pellet containing no additive. It was found that, even when the mixture was added after mixing, strong static electricity was generated in both pellets, and the antistatic agent adhered to each pellet.

When the above mixture is molded, the two slide with each other, causing separation / classification in combination with the specific gravity difference,
The problem of segregation arises.

[0015]

[Means for Solving the Problems] As a result of various studies to solve the above problems, in a mixture of a master batch pellet highly filled with an inorganic filler and a pellet for dilution, an antistatic agent was previously added only to the pellet for dilution. The present inventors have found that a polyolefin mixture in which this is added and mixed with pellets for dilution can solve all of the above problems, leading to the present invention.

That is, an inorganic filler is added to a polyolefin.
0 to 90% by weight of a polyolefin masterbatch pellet and a mixture of a polyolefin pellet for dilution, and a polyolefin mixture obtained by adding 0.01 to 2 phr of an antistatic agent to substantially only the polyolefin pellet for dilution and mixing. is there.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The term "pellet" used in the present invention refers to a pellet having an average particle size in the range of 1 mm to 10 mm. It is preferable that the difference between the average particle diameters is not so large and does not largely differ. Generally, the ratio of the respective diameters is preferably in the range of 0.7 to 1.3.

In the present invention, the concentration of the inorganic filler in the masterbatch pellets may be determined in consideration of productivity, cost and the like, but the concentration which is usually in the range of 50 to 90% by weight is optimal, and preferably 65 to 90% by weight. ８５85% by weight. When the concentration of the inorganic filler is 50% by weight or less, not only the effect of the present invention is not sufficiently exhibited, but also the transportation cost is disadvantageous. In addition, when the concentration of the inorganic filler is 90% by weight or more, productivity is lacked during the production of the master batch pellets, and poor dispersion of the inorganic filler occurs during molding of the mixture in the pellet or with the pellet for dilution, which is not preferable. .

In the present invention, as the inorganic filler,
It can be used without any particular restrictions. For example, talc, calcium carbonate, clay, silica, mica, magnesium carbonate, barium sulfate, aluminum hydroxide, magnesium hydroxide, wollastonite, glass powder, glass beads and the like. Further, fibrous magnesium oxysulfate, potassium titanate fiber, magnesium hydroxide fiber, aluminum borate fiber, calcium silicate fiber, calcium carbonate fiber and the like are listed. These inorganic fillers may be used alone or as a mixture of two or more.

The polyolefins of the masterbatch pellets and the pellets for dilution used in the present invention may be of the same type or different types.

Examples of the polyolefin include homopolymers of α-olefins such as ethylene, propylene, butene-1, hexene-1, heptene-1, and octene-1, or blocks or random copolymers of the above α-olefins. Polymers and mixtures of these polymers are listed.

Specific examples of the block or random copolymer of α-olefins include ethylene-propylene random copolymers having an ethylene content of 10% by weight or less, ethylene-propylene block copolymers, and ethylene-propylene block copolymers. Examples thereof include an ethylene-butene-1 random copolymer and an ethylene-butene-1 block copolymer having a content of 10% by weight or less.

Further, the most commonly used additives in this polyolefin include antioxidants, heat stabilizers,
You may add an ultraviolet absorber, a copper damage inhibitor, etc.

It is necessary to add an antistatic agent at a ratio of 0.01 to 2 phr to the dilution pellets constituting the present invention in order to eliminate segregation of the resulting mixture and obtain a uniform polyolefin mixture. , Preferably 0.
0.5 to 1 phr is desirable.

That is, regardless of the type of material, static electricity is generated due to contact between objects. In particular, the insulating material is strongly generated and charged. In this case, a positive charge is generated at one interface between the two materials, and a negative charge is generated at the interface between the other materials. A similar relationship exists between the masterbatch pellets and the dilution pellets constituting the present invention, and the mixture is attracted to each other by the positive and negative charges and is well mixed. At this time, the amount of charged potential is measured on the surface of the mixture based on the ratio, capacity, and the like of the two.
However, the antistatic agent of the pellet for dilution is 0.01 ph.
When the mixing ratio is less than r, the mixing pellets having good mixing properties but low specific gravity adhere to the wall surface of a handling device such as a mixer or a hopper, and the mixing ratio changes. On the other hand, 2.0p
In the case of more than hr, the charge amount of the pellet for dilution becomes small, and as a result, the above-mentioned attracting due to the static electricity disappears, and the mixing property is reduced due to the difference in specific gravity between the master batch pellet and the pellet for dilution, thereby causing separation and segregation. Also,
This makes it easier for the master batch pellets to adhere to the wall surface of the handling device. Therefore, finally, the concentration of the inorganic filler changes, resulting in a bad influence on the product quality.

As is clear from the above description, according to the present invention, static electricity is controlled by adding an antistatic agent to the pellet for dilution, segregation due to adhesion is prevented, and the controlled static electricity is used. As a result, segregation due to a difference in specific gravity from the master batch pellets can be prevented.

The method of adding the antistatic agent to the dilution pellets of the present invention is not particularly limited as long as it is a method of adding the antistatic agent before mixing with the master batch pellets. For example, any method may be used, such as a method in which the polyolefin is contained and dispersed in polyolefin to form a pellet, and an antistatic agent is applied or coated to the polyolefin in a pellet form.

As the antistatic agent to be used, any known compounds can be used without any problem. For example,
Nonionic antistatic agents such as lauryl diethanolamine, myristyl diethanolamine, palmityl diethanolamine, stearyl diethanolamine, oleyl diethanolamine, stearyl diethanolamine monostearate, stearyl diethanolamine monopalmitate, palmityl diethanolamine monopalmitate, and diethanolamide lauric acid, myristine Acid diethanolamide, palmitic acid diethanolamide, stearic acid diethanolamide, oleic acid diethanolamide, stearic acid diethanolamide monostearate and other amide-based antistatic agents and fatty acid esters of polyhydric alcohols, for example, glycerin fatty acid esters, sorbitan fatty acid esters, Pentaerythritol fatty acid ester, Polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, one or a mixture of two or more selected from ester-based antistatic agents such as polyglycerol fatty acid ester.

The mixing ratio of the master batch pellets and the dilution pellets of the present invention is not particularly limited, and may be determined in consideration of the performance of the molded article. Usually, the final inorganic filler concentration is preferably about 5 to 50% by weight. Also,
Other masterbatch pellets such as a pigment masterbatch pellet can be blended with the mixture of the masterbatch pellet and the dilution pellet of the present invention, and the mixture can be used without any problem.

[0030]

As will be understood from the above description, the polyolefin mixture of the present invention can improve the mixing accuracy of the mixture and at the same time can prevent the mixture from adhering to a mixer or a molding machine hopper. This has the effect of preventing adverse effects due to fluctuations in the ratio and, consequently, fluctuations in the quality of the product, and makes it possible to economically obtain the final product.

[0031]

EXAMPLES The present invention will be described more specifically with reference to examples, comparative examples and reference examples, but the present invention is not limited to these examples.

Examples 1 to 3 (1) Production of Polyolefin Pellets Highly Filled with Inorganic Filler 20% by weight of polypropylene and 80% by weight of talc were mixed by stirring with a high-speed stirring mixer, and then granulated by an extruder. Batch pellets were used.

(2) Production of Polyolefin Pellets for Dilution PP pellets for dilution prepared by granulating polypropylene with an antistatic agent in the amount shown in Table 1 were used.

(3) Mixing Measuring and mixing device (trade name: Micosuper SR-1 manufactured by Kubota Colortronic Co., Ltd.) with a measuring device on a molding machine hopper (material: stainless steel) having a stirring blade for mixing inside.
0) was attached to an injection molding machine and weighed and mixed at a ratio of 25% by weight of master batch pellets and 75% by weight of PP pellets for dilution so that the final talc amount was 20% by weight.

(4) Measurement of Amount of Charge Potential In order to refer to the influence of the antistatic agent, a vibration-type surface voltmeter (trade name: KDS manufactured by Kasuga Electric) was placed at a position 10 cm from the surface of the mixture obtained in (3). -0102), the maximum potential was measured and as shown in Table 1. At this time, the room temperature was 25 ° C. and the humidity was 60% RH.

(5) Molding and evaluation A length of 340 mm, a width of 220 mm, and a thickness of 4
A mold having a shape of mm was mounted and injection-molded. When 45 shots were formed from the start of the injection molding, the metering and mixing were stopped, and then the entire amount was injection-molded until the inside of the hopper became empty.

The number of the obtained plate-like injection molded products was 53. The weight of the plate thus formed is measured in the order of molding, and the initial 5 to 6 shots from the start of molding, 6 to 4
The weight variation ratio (%) was calculated by dividing the 8 shots into the middle stage of molding and the remaining 5 shots into the final stage of molding. In addition, the percentages of the plates within ± 2% from the weight average were calculated as acceptable products, and the percentages were as shown in Table 1.

Comparative Example 1 A polyolefin mixture was produced in the same manner as in Example 1 except that no antistatic agent was added to the PP pellet for dilution, and a similar test was performed on the obtained mixture. The results are shown in Table 1.

Comparative Example 2 A polyolefin mixture was prepared in the same manner as in Example 1 except that 3 phr of an antistatic agent was added to the PP pellet for dilution, and a similar test was performed on the obtained mixture.
The results are shown in Table 1.

Comparative Example 3 In Example 1, the masterbatch pellets containing no antistatic agent and the PP pellets for dilution were added to the masterbatch pellets and the PP pellets for dilution by a different measuring machine with respect to the total amount of the masterbatch pellets and the PP pellets for dilution. Then, a polyolefin mixture was produced in the same manner except that the mixture was adjusted to 1 phr and mixed, and a similar test was performed on the obtained mixture. Table 1 shows the results
Are shown together.

Reference Example 1 Master batch pellets formed by mixing 60% by weight of polypropylene and 40% by weight of talc with a high-speed stirring mixer and then granulating with an extruder were used.

The obtained masterbatch pellets are blended with PP pellets for dilution containing no antistatic agent so that the final talc content is 20% by weight, and the antistatic agent is added to 1 phr with respect to the total amount of both. A polyolefin mixture was produced in the same manner as in Example, except that the mixture was added later and mixed, and a similar test was performed on the obtained mixture.
The results are shown in Table 1.

[0043]

[Table 1]

Claims (1)

[Claims] An inorganic filler is added to a polyolefin in an amount of 50 to 50%.
A polyolefin mixture comprising a mixture of a polyolefin masterbatch pellet filled with 90% by weight and a polyolefin pellet for dilution, wherein substantially 0.01 to 2 phr of an antistatic agent is added only to the polyolefin pellet for dilution.