WO2005087862A1

WO2005087862A1 - Calcium carbonate filled polyolefin mixture

Info

Publication number: WO2005087862A1
Application number: PCT/IB2005/050845
Authority: WO
Inventors: Osman Ersoy; Neslisah Uyar; Yasin Kansu
Original assignee: Arcelik Anonim Sirketi
Priority date: 2004-03-08
Filing date: 2005-03-08
Publication date: 2005-09-22
Also published as: TR200604830T1

Abstract

This invention relates to a mixture with high impact strength, which is composed of homopolymer, copolymer and calcium carbonate and wherein it is accomplished to increase the resistance against temperature, water vapor and chemicals.

Description

Description CALCIUM CARBONATE FILLED POLYOLEFIN MIXTURE

[001] This invention relates to a mixture obtained by combining polyolefin materials with filling materials such as calcium carbonate and the like.

[002] Filled polyolefin materials are utilized in various areas such as in washing machine production, in the manufacturing process of different components such as the washing tank, detergent box, pump body and the pump chamber. Polyolefin, for example polypropylene material, is preferred due to its high chemical resistance, good mechanical strength values and low cost. It is possible to produce a cheaper material with mechanical properties suitable for the purpose of use by filling the polypropylene material with fillers and reinforcers such as talc and calcium carbonate.

[003] In order to obtain a homogenous mixture, during production procedure, filling materials are doped to the polypropylene resin at process temperatures higher than the melting temperature. During the mentioned process, as a consequence of the formation of free radicals under the effect of the temperature and shear forces and of the reaction of the said radicals with oxygen, other chemicals and polymer main chain in the environment, degradation starts at the organic portion of the mixture. The advanced stages of degradation cause breaks in the chains and/or reduction of the molecular weight and therefore reduction of the mechanical strength values, color distortions and worsening of fluidity properties. In order to prevent the degradation problem, chemical stabilizers should be added to the blend during the preparation process of the polymeric mixture.

[004] In relation to the location of use, for instance, if used as the washing tank of a washing machine, filled polyolefin materials are exposed to heat, water vapor and various chemicals (detergent, bleaching liquid, dirt particles dissolved by water during washing process etc.) during the operation. As a result of the reactions that may be led by free radicals which could be formed under the action of temperature and chemicals, deformations start to occur in the structure of the mixture. Therefore, the resistance against the afore-mentioned factors should be increased.

[005] In the current state of the art, in the United States Patent Document no. 4120844, a description is given of an application wherein a polypropylene material composed of homopolymer and copolymer mixture is blended with calcium carbonate filling material so as to increase the impact strength properties.

[006] In the current state of the art, in the British Patent Document GB 1134422, a description is given of an application wherein polymer material is mixed with two different filling materials one powder based and the other fibrous, so as to increase the flexibility. [007] In the current state of the art, in the United States Patent Document US 6642290, a description is given of producing syndiotactic polypropylene by using several nucleation agents.

[008] In the current state of the art, in the United States Patent Document US 5969027, a description is given of an application wherein a polypropylene material composed of homopolymer and block copolymer mixture is blended with calcium carbonate filling material so as to increase the impact strength properties.

[009] The aim of the present invention is the realization of a polyolefin based mixture reinforced by a filling material to reduce the cost wherein the chemical stability is increased against the aging effects of the temperature, water vapor and chemicals, the mechanical strength values are increased and the injection circulation time is reduced.

[010] The mixture according to the present invention includes a homopolymer, a filling material, a copolymer which increases the impact strength reduced by the effect of the filling material and imparts ductility to the material, a stabilizer whereby the degradation problem is prevented and a nucleation agent whereby it is achieved that solidification inside the injection mold is accelerated by increasing the crystallization speed and percentage of the semicrystalline homopolymer during the shaping process, and thereby that the injection circulation time is reduced and the agent of which is utilized to decrease the crystal diameters, to regulate the crystal structure, to hinder the penetration of solvent molecules and at the same time to prevent/retard the color yellowing by attaining a synergic interaction with the stabilizers.

[011] Preferably a semicrystalline isotactic polypropylene is used as the homopolymer.

[012] The copolymer is an ethylene-polypropylene copolymer. Preferably a block copolymer is used because it has higher impact strength and does not interact with the nucleation agent.

[013] Preferably calcium carbonate is used as the filling material.

[014] Antioxidant stabilizers whereby radicals (especially peroxy radicals) formed as a result of degradation are deactivated and which degrade the hydroperoxydes that may occur by the formation of the afore-mentioned radicals to alcohol, and/or a thiosynergist thermal stabilizer whereby long term thermal stabilization (LTTS) is accomplished and which can form a synergic interaction when used together with the antioxidant stabilizers are used as the stabilizer.

[015] Antioxidant stabilizer is a mixture of a phenolic main antioxidant as the hydrogen donor and a phosphate based secondary antioxidant as the hydroperoxide decomposer. For instance, pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate) is utilized as the phenolic main antioxidant and Tris (2,4-ditert-butylphenyl)-phosphite as the phosphate based secondary antioxidant. [016] Dioctadecyl 3,3'thiodipropionate is used as the thiosynergist thermal stabilizer.

[017] Sodium salts, preferably sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate, are utilized as the nucleation agent.

[018] In another application of the present invention, the mixture includes calcium stearate with acid binding properties which increases the effectiveness of the stabilizer and reduces the friction between the mixture and the mixers at temperatures above the melting temperature of the polymer.

[019] The mixture is prepared by combining the homopolymer, the calcium carbonate that is used to cheapen the material, the ethylene-polypropylene block copolymer which is used to increase the impact strength and to impart ductility and impact strength at desired proportions to the material, stabilization agents and the nucleation agent (sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate) together as in powder or granule form and then by blending at a temperature higher than the melting temperature of the polymer under the application of a considerable shear force.

[020] The nucleation agent (sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate) decreases the crystallization time of the polymers in the mixture and induces reduction of the crystal diameters and well-arrangement of the crystal structure. By means of the said reduction of the diameters and the fact that the structure is more homogenous, it is achieved that the strength of the mixture is increased. As the nucleation agent increases the speed of crystallization, the solidification time of the polymer that is injected into the mold in melt form decreases. This in turn increases production speed since plastic material can be removed from the mold faster.

[021] While preparing the mixture, particularly the remainders of the catalysts (TiC13, A1(C2H5)2C1) used during the synthesis of the polyolefin material cause acidic compounds to form inside polymer by catalyzing hydroperoxide decomposition. The calcium stearate (CaSt) that is used as the acid binding component, converts the acid into the calcium chloride salt (CaC12) by reacting with the mentioned acid formed in the polymer. Because of the hygroscopic and water-soluble properties of calcium chloride, if the polymer is exposed to water vapor and hot water detergent solution, hydroperoxide decomposition may again be catalyzed by the formation of acidic compounds and antioxidant consumption may be accelerated. As the hydroperoxide transforms into a non-radical form by obtaining one hydrogen from the antioxidant, the phenolic antioxidant that loses its hydrogen turns into a quinonic structure. The quinone compound is a colored compound due to the chromophore group it contains and causes the polymer to yellow. It is considered that some part of the CI^" ions that form as a result of the CAC12 decomposition generates acidic compounds by reacting again with water and some other part prevents the formation of more amount of acidic compounds by reacting with the Na⁺¹ ion which is present in the structure of the nucleation agent (sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate). Furthermore, some portion of the nucleation agents retards the penetration of the solvent molecules into the material by regulating the crystal structure of the polymer. Therefore, the inner structure is protected from the degradation effects also physically. For the said reasons, it is considered that the nucleation agents containing Na⁺ ion, used together with the antioxidants, ensures a synergic protection against the negative aging effects of the environment in a situation where the mixture is exposed to water vapor and hot water detergent solution.

[022] Various experiments are conducted in order to be able to understand the effects of the mixture in accordance with the present invention on the parameters aimed to be improved.

[023] EXPERIMENT

[024] Experiments are conducted by forming several calcium carbonate filled polyolefin mixtures with different formulations in order to prove that the fact that the yellowing of the color is prevented/retarded which fact is considered to stem from the synergic interaction of the nucleation agent (sodium 2,2'-methylene bis- (4,6-di-tert-butylphenyl) phosphate) with the acid binders, the antioxidants and thermal stabilizers added to the mixture, actually occurs because of the mentioned chemical.

[025] The first mixture (Ml) used in the experiments contains homopolymer and calcium carbonate; the second mixture (M2) contains homopolymer, copolymer and calcium carbonate; the third mixture (M3) contains homopolymer, copolymer, calcium carbonate, calcium stearate and stabilizers; and the fourth mixture (M4) contains 52.74 % homopolymer, 5.86% copolymer, 40 % CaCO3 filled polypropylene, 0.5 % CaSt, 0.3 % antioxidant stabilization agent (composed of 50 % Tris (2,4-ditert-butylphenyl)-phosphite and 50 % pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate), by weight), 0.3 % thiosynergist process stabilizer (dioctadecyl 3,3'thiodipropionate) and 0.3 % nucleation agent (sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate), where all percentages are given in weight percentages. The following are manufactured from that mixture by injection method; tension specimens according to ISO R527 standards, bending and impact specimens according to ISO 180 standards, and a plate with 80x80x2 mm dimensions used for color measurements. Before the aging test; tension, impact strength and elongation tests are applied to some of the specimens. Some of the specimens are subjected to aging test in a 1% detergent solution at 90 °C, some other . part in a stove at 100 °C and the rest in water vapor at 100 °C for 1 month and after the aging tests mechanical and color measurement tests are performed. Particularly after the 15th day, it is detected that there is a considerable increase at the yellowing index of the specimens (Ml, M2, M3) except for the specimens (M4) that contain sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate and are subjected to a 1% detergent solution at 90 °C and to water vapor at 100 °C. For the specimens left in the stove at 100 °C, no considerable difference is noted between the specimens (M4) that contain sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate and the ones (M3) that do not contain such. The observation of the effects of the nucleation agent which prevents/retards the yellowing of the color in media under the conditions of high temperature and especially existence of water, proves that the mechanism considered after the early trials does actually work. The mixture proportions used and the results of the experiments are illustrated in Table 1.

TABLE 1

By means of the application according to the present invention, by utilizing the nucleation agent inside the mixture, it is achieved to reduce the total injection circulation time, to increase the mechanical strengths and, to retard the increase at the yellowing of color of the polymeric material thanks to the synergic interaction generated by incorporating the said agent with other stabilizers against the conditions which the material is exposed to in the media of washers as explained before.

Claims

[001] 1 - A mixture including; a homopolymer, a filling material, a copolymer which increases the impact strength reduced by the effect of the filling material and imparts ductility to the material, a stabilizer whereby the degradation problem is prevented and a nucleation agent whereby it is achieved that solidification inside the injection mold be accelerated by increasing the crystallization speed and percentage of the semicrystalline homopolymer during the shaping process, and thereby that the injection circulation time be reduced, and characterized by a sodium-salts-based nucleation agent which is utilized to decrease the crystal diameters, to regulate the crystal structure, to hinder the penetration of solvent molecules and at the same time to prevent/retard the color yellowing by attaining a synergic interaction with the stabilizers.

[002] A mixture as described in any one of the above Claims, wherein the homopolymer is a semicrystalline isotactic polypropylene.

[003] A mixture as described in any of the above Claims, wherein the copolymer is an ethylene-polypropylene copolymer.

[004] A mixture as described in any of the above Claims, wherein the copolymer is a block copolymer which has higher impact strength and does not interact with the nucleation agent.

[005] A mixture as described in any of the above Claims, wherein the filling material is calcium carbonate.

[006] A mixture as described in any of the above Claims, characterized by an antioxidant stabilizer whereby radicals (especially peroxy radicals) formed as a result of degradation are deactivated and which degrade the hydroperoxydes that may occur by the formation of the afore-mentioned radicals to alcohol.

[007] A mixture as described in Claim 6, characterized by an antioxidant stabilizer which is composed of a phenolic main antioxidant as the hydrogen donor and a phosphate based secondary antioxidant as the hydroperoxide decomposer.

[008] A mixture as described in Claim 7, characterized by an antioxidant stabilizer including a mixture of Tris (2,4-ditert-butylphenyl)-phosphite and pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate) .

[009] A mixture as described in Claims 6-8, characterized by a thiosynergist thermal stabilizer whereby long term thermal stabilization (LTTS) is accomplished and which can form a synergic interaction when used together with the antioxidant stabilizers.

[010] A mixture as described in Claim 9, wherein the thiosynergist thermal stabilizer is dioctadecyl 3,3'thiodipropionate. [011] A mixture as described in any of the above Claims, comprising calcium stearate with acid binding properties which increases the effectiveness of the stabilizer and reduces the friction between the mixture and the mixers at temperatures above the melting temperature of the polymer.

[012] A mixture as described in any of the above Claims, wherein sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate is utilized as the nucleation agent.

[013] A polymer material based item wherein the said polymer material is produced by using a mixture as described in any of the above Claims.