JPS6037823B2 - Resin composition for injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In injection molding, the present invention utilizes the excellent physical properties inherent to resins [e.g., environmental stress cracking resistance (Envjro
mentaIStressCrackingResiS
(hereinafter referred to as "ESCR").

], relates to a polyolefin resin composition for the purpose of maintaining appearance performance and preventing carbide generated in an injection cylinder from being mixed into a molded product. In injection molding, if foreign substances such as carbide are mixed into the raw resin, naturally the foreign substances such as carbide will be mixed into the molded product.

However, even when raw resins containing no foreign substances such as carbides are used, carbides are found to be mixed into molded products, significantly reducing the commercial value of the molded products and, in some cases, resulting in defective products. . This phenomenon is thought to be due to oxidative deterioration of the raw resin in the injection cylinder due to heat.

In other words, a part of the raw resin plasticized in the injection cylinder stays and adheres to the metal surface of the screw, barrel, etc., is oxidized by the heat of the heater, and carbonizes and turns into a carbide-causing substance. The carbide of this resin (hereinafter referred to as “
It is thought that the molded product is mixed with molded products during injection molding. The contamination of molded products with heat sludge is a phenomenon that occurs very often during injection molding when the cylinder temperature is raised and the molding operation is started.

Currently, the means to prevent burn marks from entering the molded product during injection molding are (1) Using resin to which antioxidants have been added to prevent thermal oxidation of the resin, which is the direct cause of burn marks. .

■ A screen pack is installed at the tip of the injection cylinder of the injection molding machine to remove foreign substances mixed in the resin (Tsubaki Sekisho 54-
117560).

{3} Injection molding is performed at a low molding temperature to reduce the degree of thermal oxidation of the resin, which causes burnt spots.

etc.

However, with regard to the method (1), the addition amount of the commonly used antioxidant is not effective against the phenomenon of the occurrence of heat sludge. The effect of increasing the amount added was also examined, but it was not possible to prevent the occurrence of heat sludge. Regarding the means for [2], Japanese Patent Application Laid-Open No. 54-117560 discloses a technique for removing carbon particles by installing a screen pack at the tip of the injection cylinder of an injection molding machine, but the screen pack significantly reduces the injection function. Furthermore, the screen pack has the disadvantage that the screen pack must be replaced after a certain period of time due to clogging. Furthermore, it is not easy and technically difficult to attach the screen pack to the general-purpose injection molding machines currently in use. Regarding the method of {3--, it is thought that when injection molding is performed at a low molding temperature, the thermal oxidation effect on the resin used is small, and naturally the amount of burnt burns generated should be small. However, when compared with the case where injection molding was actually performed at a high molding temperature, the amount of burnt sludge produced was slightly smaller when injection molding was performed at a lower molding temperature. Furthermore, injection molded products made at lower molding temperatures have the disadvantage that ESCR, which is one of the important physical properties, is lower than injection molded products made at high molding temperatures. As a result of the above, at present, without any effective countermeasures, resin is supplied into the injection cylinder to clean it until the generation of heat loss stops, but this cleaning operation significantly reduces productivity. ing. In view of the above-mentioned problems, the inventors of the present invention, as a result of research, have surprisingly found that all of the above-mentioned drawbacks can be solved by simply adding a very small amount of a complete ester of polyhydric alcohol and fatty acid. This led to the present invention.

That is, in the present invention, the complete ester shown in formula (1) is reduced to 0.
The present invention relates to a polyolefin injection molding resin composition containing 1 to 2.0% by weight. The present invention will be further described below with respect to the residues removed.

The complete ester used in the present invention is represented by the above general formula (1), and the complete ester referred to herein is different from the partial ester, and refers to one in which all -OH groups of the polyhydric alcohol are esterified.

Here, X is a residue obtained by removing the -OH group from a polyhydric alcohol, and examples of the polyhydric alcohol having 3 to 8 -OH groups include glycerin, bentaerythritol, solpit, mannitol, Examples include sorbitan, mannitan, and sucrose.

In addition, xf○FRo-○nam]blood in the general formula is a residue obtained by removing the terminal hydrogen from an oxyethylene adduct of a polyhydric alcohol having 3 to 8 monoOH groups, and Representative examples of the oxyethylene adduct of polyhydric alcohol No. 8 include polyoxyethylene glycerin ether, polyoxyethylene sorbitan ether, and the like.

○Also, -△Y in the general formula is a residue obtained by removing one OH group from a fatty acid or a hydroxy fatty acid. acids, behenic acid, lignoceric acid, etc. Hydroxy fatty acids include Q-hydroxyisobutyric acid, 8-hydroxypropionic acid, DL-Q-hydroxyisocaproic acid, 3-hydroxymyristic acid,
2-hydroxypalmitic acid, ricinoleic acid, 8,9-
Examples include dihydroxystearic acid, 12-hydroxystearic acid, and the like.

Complete esters obtained from this include, for example, palmitic acid triglyceride, stearic acid triglyceride,
Sorbitan tetrastearate, 12-hydro.

xystearic acid triglyceride, sorbitan tetra 12-hydroxystearate, monostearic acid di1
2-hydroxystearic acid triglyceride, polyoxyethylene glycerin tristearate, polyoxyethylene glycerin tri-12-hydroxystearate, polyoxyethylene sorbitan tetrastearate,
Examples include polyoxyethylene sorbitan tetra-12-hydroxystearate, monostearic acid di-12-hydroxystearic acid polyoxyethylene triglyceride, and the like. Among them, 12-hydroxystearic acid triglyceride obtained by completely hydrogenating ricinoleic acid ester of glycerin, which is the main component of castor oil, which exists as a natural vegetable oil, is more effective for the purpose of the present invention, and is industrially and economically advantageous. It is particularly useful from this point of view. Mixtures of these are also useful. These complete esters have a ratio of 0.1 to 2.0% relative to the polyolefin resin. % by weight can be used.

Preferably 0.3-1. % by weight. 0.1% by weight
If it is less than 2., there is no effect of preventing the contamination of brown moss. If the weight percentage exceeds , the appearance performance deteriorates and the ESCR may also decrease.

Furthermore, partial esters do not have the effect of preventing the contamination of burnt moss.
In the present invention, polyolefin resin is used.

Particularly preferred are polyethylene, polypropylene, copolymers of ethylene or propylene with other Q-olefins, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, ethylene-ethyl acrylate copolymers, and Examples include metal salts of ethylene and unsaturated carboxylic acids, such as zinc or sodium salts of ethylene-acrylic acid copolymers.

Among these, polyethylene and ethylene-vinyl acetate copolymers are particularly useful. Mixtures of these are also useful. A more preferable melt index (ASTM-D-1238 Condition E) of polyolefin resin is:
The range is from 0.1 to 70 evenings/10 minutes. Particularly preferred is 0.2 to 20 evenings/10 minutes. In the present invention, the above general formula (
There are no particular restrictions on the method for adding the perfect ester shown in 1) to a polyolefin resin to obtain a resin composition for injection molding, but for example, an extruder, a roll mill, or a Banbury mixer commonly used for kneading polyolefin resins can be used. There is a method of kneading using the above general formula (1
) It is also possible to search for a masterbatch form containing a high concentration of complete wastes and add it diluted.

Moreover, the complete ester shown in the above-mentioned general procedure 1) may be melted and press-fitted from an intermediate position of the extruder.

Any method of addition may be used. Antioxidants, ultraviolet absorbers, coloring dyes and pigments, etc. may be added to the composition of the present invention, if necessary.

Injection molding in the present invention includes injection molding using a so-called general injection molding machine, injection blow molding using a blow molding machine equipped with an injection function, and the like.

The evaluation method and evaluation scale used in the present invention are shown below.

The effects of the present invention are compared with the degree of contamination of heat deposits in injection molded products and E.
Evaluate based on SCR and molded product appearance.

{i) Degree of contamination with heat deposits The resin composition, which is a sample, was continuously molded into 5-sized flat plates (size: 15 x 15 x 2, thickness: 2 sides) by injection molding, and the interior of each plate was Using a spot size gauge (wireless communication equipment industry standard), the amount of brown moss mixed in is measured as the turbidity point number.

Next, the size and number of turbidity points are shown. The number of turbidities of each size inside the flat plate is measured, the number is multiplied by the score, the total score is obtained, and this is used as the turbidity score of the flat plate molded product.

Furthermore, the average turbidity point number of the fork of the flat plate 5 is calculated. The average turbidity point is compared with the amount of defective products, and the scale of the degree of contamination is shown below.

{B) ESCR Form the same flat plate as described in (a).

The test piece was made from this flat plate according to ASTM-D-1693 (ESC
ESCR was evaluated under the following conditions according to the same method. Reagent Liponox NC1 (Lion Oil proprietary nonionic surfactant) 0.5%
Aqueous solution environmental temperature 5000 Test piece n number Time until cracks appear in 50% of 2 solid test pieces in 2 boxes (F
50) was measured.

The value and determination of this F50 are shown below. Shiichi Molded product appearance {
Form the same flat plate as described in section A.

The following relative evaluation is performed using this flat plate. In the evaluation scales of Jōgonki [i], {guchi}, and shiichi, if there is even one item with the code X, it is considered to be a practical problem.

The present invention will be explained in more detail with reference to the following examples and comparative examples.

Examples 1 to 6 and Comparative Examples 1 to 5 The resin compositions shown in Table 1 and Table 2 were applied to an injection molding machine (an in-line screw injection molding machine manufactured by Toshiba Machinery Co., Ltd.) that reached the cylinder temperature shown in the table. After completely replacing the inside of the injection cylinder with the resin compositions shown in Tables 1 and 2, the heater was turned off and the cylinder temperature was allowed to cool to about 30 qC.

Next, set the cylinder temperature again to the temperature shown in the table and turn on the heater. Immediately after reaching the set temperature, injection molding was performed continuously using a flat plate mold (film gate) measuring 15 mm x 15 mm and having a thickness of 2 to obtain 52 flat plate molded products. The first consecutive 50 of the 52 female flat plate molded products.
Evaluate the degree of contamination with a sheet of paper, and then evaluate the degree of contamination with E.
The SCR was evaluated, and the remaining one sheet was evaluated for the appearance of the molded product.

The evaluation results are shown in Tables 1 and 2.

Using the composition containing the complete ester shown in the example,
The flat plate obtained by injection molding had a good ESCR and a good appearance of the molded product, and there were no defective products due to inclusion of heat deposits, giving very good results.

Additives and resins used in Examples and Comparative Examples are described below. (Additive) y 12-hydroxystearic acid triglyceride (
Made by NOF ■: Castor Wax A) ■ Stearic acid triglyceride (Made by NOF ■: Extremely hardened beef tallow oil) ■
Tetrakis [methylene-3-(3,5'-di-t-butyl 4-hydroxyphenyl)propionate] methane (manufactured by Ciba-Geigy: Irganox 1010) ■ Stearic acid monoglyceride (manufactured by NOF ■: Monogly M old)
(Resin) ■ M-2115: Low density polyethylene (density 0.92
As is clear from the above examples, according to the present invention, excellent physical properties (ESCR) and appearance performance are maintained, and injection molding is possible. A highly economical resin composition that can reduce the amount of heat sludge mixed into molded products has extremely great industrial value.

Table-1 Table-2

Claims (1)

[Claims] 1. A complete ester represented by the following general formula (I) with 0.
A polyolefin injection molding resin composition containing 1 to 2.0% by weight. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ X: Residue from polyhydric alcohol with -OH group removed no
: The number of -OH groups in the polyhydric alcohol, a positive integer of 3 to 8 Ro: A hydrocarbon group having 1 to 5 carbon atoms, including isomers m: O or a positive integer of 1 to 7 Y : Residues from hydrocarbon groups with 11 to 23 carbon atoms and/or hydroxy fatty acids, excluding ▲numerical formulas, chemical formulas, tables, etc.▼