JPH0460498B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a crystalline polyolefin resin composition. [Prior Art] Compounds represented by the general formula () or () are used as nucleating agents for crystalline polyolefin resins, and are effective in improving rigidity and shortening molding cycles, and improve the transparency of molded products. (Polymer Processing, Vol. 35, No. 1)
No., pp. 30-35 (1986)). [Problems to be Solved by the Invention] However, conventional nucleating agents have poor solubility in resins, particles aggregate, and dispersibility is not very good. In addition, during molding, it is necessary to raise the temperature above the melting point of the nucleating agent to dissolve the nucleating agent in the resin, but under such temperature conditions the nucleating agent sublimates, causing dirt on the processing machine and molded products. This causes various problems in terms of quality and work, such as stains and the generation of odors. Although various attempts have been made to apply various additives to solve these problems, it cannot be said that an effective method has been established yet. [Means for Solving the Problems] As a result of intensive studies to fundamentally improve these drawbacks, the present inventor found that the freeze-dried products of conventional nucleating agents have a unique microstructure, and that they are suitable for use as nucleating agents. It was discovered that the intended purpose could be achieved without impairing functionality, and the present invention was completed based on this knowledge. That is, an object of the present invention is to provide a novel crystalline polyolefin resin composition characterized in that it contains a freeze-dried product of a compound represented by the following general formula () or (). (In the formula, X, X', X'' are hydrogen atoms, carbon numbers 1 to 3
an alkyl group having 1 to 3 carbon atoms, a halogen atom, n is an integer of 1 to 5, p is 0 or 1) The nucleating agent represented by the general formula () or () according to the present invention is It is a compound obtained by condensing an aromatic aldehyde and a polyhydric alcohol having a valence of 5 or more. Examples of the aromatic aldehyde include benzaldehyde, benzaldehyde substituted with 1 to 5 alkyl groups having 1 to 3 carbon atoms, and 1 to 5 halogen atoms.
5-substituted benzaldehyde substituted product, carbon number 1
Examples include benzaldehyde substituted products having 1 to 3 alkoxy groups substituted with 1 to 5 alkoxy groups, and mixtures thereof in arbitrary proportions. Examples of polyhydric alcohols include sugar alcohols such as sorbitol and xylitol, and mixtures thereof in arbitrary proportions. The resulting nucleating agent includes the type of each aromatic substituent,
It includes not only different numbers of asymmetric types or the same target type, but also mixtures thereof, as well as arbitrary mixtures of sorbit derivatives and xyrite derivatives. It is a well-known fact that the compound represented by the general formula () or () has the ability to gel water or various organic solvents, and the lyophilized product of the nucleating agent according to the present invention is the gelled product. It can be obtained by freezing and drying under reduced pressure. The organic solvent may be any solvent that can be gelled and frozen by the compound, and specific examples include dioxane, benzene, xylene, dichlorobenzene, cyclohexanol, and ethylenediamine. Based on X-ray analysis, this material retains the microstructure at the time of gel formation even after the gel medium is removed by vacuum drying, and it is inferred that the apparent spacing is different from the conventional crystalline structure. be done. For example, 1,3,2,4-bis-(dimethylbenzylidene) sorbitol (hereinafter referred to as Me-DBS)
In the case of crystals of
In the Me-DBS gel and its lyophilized product, the maximum diffraction intensity peak is at 2θ = 3.2 to 3.3 degrees. As a result, it exhibits a very low apparent specific gravity compared to conventional nucleating agents and has an increased surface area, making it possible to disperse and dissolve into resin at lower temperatures, which is thought to produce the desired effect. . In addition, the particle size is smaller than that of conventional nucleating agents having the same type of structure, and the particle size can be controlled arbitrarily. The apparent specific gravity of the freeze-dried product itself is less than 0.1, which is very low compared to 0.2 to 0.5 for conventional nucleating agents, but due to the design of the product, the powder is compressed to the same level as conventional products. It can also be adjusted. however,
Even in this case, the above-mentioned gel structure is microscopically maintained and the desired properties remain unchanged. Examples of crystalline polyolefin resins that can achieve the effects of the present invention by blending the above compounds include homopolymers or copolymers of polyethylene, polypropylene, polybutadiene, and polyisoprene. Items with a total content of ethylene, propylene, butadiene, isoprene, etc. of 50% or more are listed. As monomers that can form copolymers with polyolefins, any of various monomers that can be copolymerized with polyolefins can be used. Specifically, vinyl acetate, acrylates, methacrylates, α-
Examples include olefins (butene, propylene, hexene, octene, etc.). The amount of the nucleating agent according to the present invention added to the crystalline polyolefin resin is not particularly limited, but is 0.03 to 3
The amount is preferably 0.05 to 2% by weight, and the desired effects of the present invention can be sufficiently exhibited by blending within this range. The present invention uses the general formula () or () as a nucleating agent.
It is carried out according to a conventional method except for blending the freeze-dried product of the compound, and the method of blending the above compound can also be carried out in the same manner as the blending of known nucleating agents. For example, it may be directly blended into powdered resin pellets, or it may be blended with resin in advance and made into pellets. In blending these ingredients, a conventional mixing machine such as a Henschel mixer, a Banbury mixer, an extruder, or a roller can be used, as is the case with conventional methods. The molding operation after compounding can be carried out by heating under temperature conditions that melt the resin, according to a conventional method. Furthermore, when molding the above resin, there is no problem in adding commonly used stabilizers, dispersants, pigments, blowing agents, lubricants, etc., or adding high density polyethylene, polypropylene, polybutene, polybutadiene, etc. Furthermore, if a polymerization catalyst remains in the polymer, it is effective to add a metal soap to neutralize it. [Example] The present invention will be described below with reference to Examples and Comparative Examples. In addition, the apparent specific gravity shown in each example below,
The degree of haze (%), crystallization temperature (°C), and degree of dispersion of the nucleating agent were measured according to the following methods. (1) Apparent specific gravity: Put a sample of known weight into a 200ml graduated cylinder, tap it 100 times, calculate the apparent specific gravity from the volume, and use the average value of the five times. (2) Haze (%): Based on ASTM D1003-52. (3) Crystallization temperature (°C): 250°C x 3 using DSC
After a few minutes, it was cooled at a rate of 15°C/min and measured. (4) Dispersion degree of nucleating agent: The dispersion state of the nucleating agent was visually observed. 〇 = No undispersed matter, × = Undispersed matter Example 1 A gel was prepared by adding 3% Me-DBS (melting point 260°C) to dioxane, and freeze-dried under high vacuum at a temperature of 0°C. A freeze-dried product of Me-DBS (hereinafter referred to as FD.Me-DBS) was obtained. The apparent specific gravity of this material was 0.10. 0.1 part by weight of calcium behenate to 100 parts by weight of homopolypropylene powder with a molecular weight of 60,000, 3.5 parts by weight
-0.06 parts by weight of di-t-butylhydroxytoluene and 0.25 parts by weight of FD・Me-DBS were dry blended in a Henschel mixer for 5 minutes, then melted at 200°C using a granulator, cooled, and cut into Pellets were prepared. Pour this pellet at 190℃ x 5
After press molding at 50Kg/ ^cm2 , cooled with water to a thickness of 1mm.
A test piece was obtained. Table 1 lists the haze, crystallization temperature, and dispersion degree of the nucleating agent measured for the obtained test piece. Comparative example 1 Me with apparent specific gravity 0.3 instead of FD/Me-DBS
Table 1 shows the results of evaluation in the same manner as in Example 1 except that -DBS was used. Example 2 A gel was prepared by adding 1.5% dibenzylidene sorbitol (hereinafter referred to as DBS) (melting point 220°C) to benzene, and freeze-dried in high vacuum at -20°C to freeze DBS. Dry products (hereinafter referred to as FD・
(referred to as DBS). The apparent specific gravity of FD/DBS was 0.08. Linear low-density polyethylene powder with a molecular weight of 100,000
100 parts by weight, 0.1 part by weight of sodium stearate, 0.06 part by weight of 3,5-di-t-butylhydroxytoluene, and 0.1 part by weight of FD/DBS were dry-blended for 5 minutes in a Henschel mixer, and then transferred to a granulator. Pellets were prepared by extrusion at 170°C.
This pellet was press-molded at 170° C. for 5 minutes at 50 kg/cm ² and then cooled with water to obtain a test piece with a thickness of 1 mm. Table 1 lists the haze, crystallization temperature, and dispersion degree of the nucleating agent measured for the obtained test piece. Comparative Example 2 Table 1 shows the results of evaluation in the same manner as in Example 2, except that DBS with an apparent specific gravity of 0.3 was used instead of FD/DBS. Comparative Example 3 In Example 1, the haze and crystallization temperature of the composition to which no nucleating agent was added were measured. In this case, as a matter of course, there is no undispersed material of the nucleating agent. Example 3 The same resin composition as in Example 2 was used as the raw material except that FD/Me-DBS was used instead of FD/DBS, and an injection molding test machine was used to perform injection at a resin temperature of 220°C, a mold temperature of 50°C, and Continuous molding of small cups was carried out under a pressure of 1500 g/cm ² . After starting injection molding,
Table 2 shows the time taken until staining due to bleeding occurs on the surface of the molded article. Example 4 Instead of FD/Me-DBS in Example 3
Bleed occurrence time was measured when using FD/DBS. The results are shown in Table 2. Comparative Examples 4 to 6 When no nucleating agent was added (Comparative Example 4), when Me-DBS was used in place of FD/Me-DBS in Example 3 (Comparative Example 5), and when FD/Me-DBS in Example 4 was used.
When using DBS instead of DBS (Comparative Example 6)
The bleed occurrence time was measured. The results are shown in Table 2. [Effect of the invention] The compound according to the present invention obtained by freeze-drying a gelled product prepared from a condensate of a specific aromatic aldehyde and a polyhydric alcohol of 5 or more valences Because it maintains its microstructure, it improves dispersion and solubility in resins when used as a nucleating agent, and can be used at temperatures below the application temperature of conventional nucleating agents. Therefore, there is less scattering due to sublimation of the nucleating agent, and the function as a nucleating agent is not impaired in any way, and contamination of processing machines and molded products is suppressed, making it possible to improve the environment and work efficiency. , its industrial value is extremely large.

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Claims (1)

[Scope of Claims] 1. A crystalline polyolefin-based resin composition comprising a freeze-dried product of a compound represented by the following general formula () or (). (In the formula, X, X', X'' are hydrogen atoms, carbon numbers 1 to 3
alkyl group, alkoxy group having 1 to 3 carbon atoms, halogen atom, n is an integer of 1 to 5, p is 0 or 1)