Polyethylene composite material for a height adjustment pad and a method for preparing the same

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a polyethylene composite material for height adjusting pad plates and a preparation method thereof. The composite material is prepared from the following components: HDPE resin, HSMPP resin, modified calcium sulfate whisker, toughening agent, lubricant, antioxidant, anti-UV additive and color master batch, is uniformly mixed, melt-extruded, then is drawn, cooled and cut into particles. Through surface treatment of the calcium sulfate whisker, the application obtains a filler which is easy to disperse and has good compatibility with polyethylene and ethylene-vinyl acetate copolymer, and the filler can greatly improve the rigidity of the material at a low addition amount, and meets various environmental use requirements. Through modification of the calcium sulfate whisker, the application obtains a height adjusting pad plate material which has a balance between rigidity and toughness, excellent bulk sampling performance and a high cost performance, and solves the potential demand in the industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a polyethylene composite material for height adjusting pad plates and a preparation method thereof. BACKGROUND

[0002] High-density polyethylene (HDPE) is a white powder or granular product. It is non-toxic and odorless, has a crystallinity of 80%-90%, a softening point of 125-135 DEG C, and a use temperature of up to 100 DEG C. It has good wear resistance, electrical insulation, toughness and cold resistance; good chemical stability, insoluble in any organic solvent at room temperature, resistant to corrosion of acids, alkalis and various salts; low water absorption; poor aging resistance and poor environmental stress cracking resistance, especially thermal oxidation can reduce its performance, so the resin needs to be modified to improve the deficiencies.

[0003] Currently, the material of the height adjusting pad plate for a rail fastening system is mainly high-density polyethylene, and the product thickness range is large, with a minimum thickness of 0.5 mm and a maximum thickness of 20 mm. The height adjusting pad plate is produced by injection molding. After injection molding of the thinner product, the performance and appearance of the sample are good, but the thicker product is seriously shrunk after injection molding, the performance of the sample is unstable, and especially the elongation at break and tensile strength are low. The HDPE pad plate product also has low heat resistance and is easily deformed at high temperature and high pressure, which limits its application range. SUMMARY

[0004] The application aims to provide a polyethylene composite material for height adjusting pad plates and a resin preparation method thereof, which has high rigidity, environmental stress cracking resistance, easy processing and stable shrinkage.

[0005] To achieve the above purpose, the polyethylene composite material for height adjusting pad plates is prepared from the following components by weight:

[0006] HDPE resin 55-90 parts, HSMPP resin 0.1-15 parts, modified calcium sulfate whisker 1-15 parts, toughening agent 5-15 parts, lubricant 0.1-1 part, antioxidant 0.1-0.5 part, anti-UV additive 0.1-0.5 part and color master batch 0.1-1 part;

[0007] The modified calcium sulfate whisker is prepared from the following components by weight:

[0008] Calcium sulfate whisker 0.6-14.5 parts, oxidized polyethylene wax 0.1-1 part and stearic acid 0.1-0.5 part.

[0009] Optionally, the polyethylene composite material for height adjusting pad plates is prepared from the following components by weight:

[0010] HDPE resin 68 parts, HSMPP resin 10 parts, modified calcium sulfate whisker 10 parts, toughening agent 10 parts, lubricant 0.3 parts, antioxidant 0.4 parts, anti-UV additive 0.3 parts and color master batch 1 part.

[0011] Optionally, the modified calcium sulfate whisker is made of the following components by weight:

[0012] Calcium sulfate whisker 9.4 parts, oxidized polyethylene wax 0.4 parts and stearic acid 0.2 parts.

[0013] Optionally, the preparation method of the modified calcium sulfate whisker comprises the following steps:

[0014] The calcium sulfate whisker, oxidized polyethylene wax and stearic acid are weighed by parts;

[0015] First, the oxidized polyethylene wax is crushed and dissolved in an organic solvent, then the calcium sulfate whisker is added, heated and stirred for a period of time, then hot filtered, and the filter cake is dispersed in anhydrous ethanol solution; finally, anhydrous ethanol solution of stearic acid is added, heated and stirred, and after the reaction is completed, filtered and dried to obtain the modified calcium sulfate whisker.

[0016] Optionally, the toughening agent is ethylene-octene copolymer and ethylene-vinyl acetate copolymer in a weight ratio of 1:1.

[0017] Optionally, the antioxidant is antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0018] Optionally, the anti-UV additive is one or more of 3808PP5, UV3346 and UV9900.

[0019] Optionally, the HDPE resin has a melt index of 0.1-4 g / 10 min and an environmental stress cracking resistance greater than 1000 h; and the HSMPP resin is a high melt strength polypropylene containing more branched structures.

[0020] A preparation method of a polyethylene composite material for a height adjustment pad, comprising the following steps:

[0021] The HDPE resin, HSMPP resin, modified calcium sulfate whisker, toughening agent, lubricant, antioxidant, anti-UV additive and color master batch are mixed uniformly, melt extruded, then drawn, cooled and pelletized to obtain the polyethylene composite material for the height adjustment pad.

[0022] Optionally, the melt extrusion step is: using a twin-screw extruder with a working temperature of 170-220℃ and a vacuum degree not greater than -0.06 MPa.

[0023] The beneficial effects of the present application are: the present application obtains a filler which is easy to disperse and has good compatibility with polyethylene and ethylene-vinyl acetate copolymer by surface treatment of calcium sulfate whiskers, and can greatly improve the rigidity of the material at a lower addition amount, meeting the use requirements in various environments; the present application obtains a material for height adjustment pad which has a good rigidity-toughness balance, excellent bulk sampling performance and high cost performance by modifying calcium sulfate whiskers, solving the potential needs in the industry.

[0024] In order to improve the material performance, on the basis of the current commonly used stearic acid treatment of calcium sulfate whiskers, the present application proposes to use oxidized polyethylene wax synergistically, which forms adsorption with calcium sulfate whiskers, and at the same time, the un-adsorbed stretched polyethylene molecular chain forms molecular chain entanglement or eutectic action with the polyethylene resin molecular chain of the matrix, thereby greatly improving the force between the whisker and the matrix resin, and further improving the material performance. Only stearic acid cannot achieve the above-mentioned effect.

[0025] The HDPE composition for height adjustment pad of the present application can effectively improve the toughness of the material and the bulk sampling elongation at break by adding the toughening agent composed of ethylene-octene copolymer and ethylene-vinyl acetate copolymer. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with specific examples.

[0027] Example 1

[0028] ① 0.4 parts of oxidized polyethylene wax is crushed and dispersed in a tetrahydrofuran solution, then 9.4 parts of calcium sulfate whisker is added, stirred at 50-100℃ for 2-12h, filtered, and the filter cake is dispersed in anhydrous ethanol solution, then anhydrous ethanol solution containing 0.2 parts of stearic acid is added, and the mixture is continuously stirred at 50-100℃ for 2-12h, and finally the mixture is filtered and dried to obtain modified calcium sulfate whisker;

[0029] ② 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV additive 3808PP5, 1 part of color masterbatch PE2718, and 5 parts of modified calcium sulfate whisker obtained in step ① are uniformly mixed, then melt-extruded in a twin-screw extruder, then drawn, cooled and pelletized to obtain a polyethylene composite material for height adjustment pad. The working temperature of the twin-screw extruder is controlled at 170-220℃, and the vacuum degree is not greater than -0.06MPa.

[0030] Example 2:

[0031] A polyethylene composite material for a height-adjusting pad plate was prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV aid 3808PP5, 1 part of color master batch PE2718, and 10 parts of the modified calcium sulfate whisker obtained in Example 1, uniformly mixing, adding into a twin-screw extruder for melt extrusion, then drawing, cooling, and pelletizing. The working temperature of the twin-screw extruder was controlled to be 170-220°C, and the vacuum degree was not greater than -0.06 MPa.

[0032] Example 3

[0033] A polyethylene composite material for a height-adjusting pad plate was prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV aid 3808PP5, 1 part of color master batch PE2718, and 15 parts of the modified calcium sulfate whisker obtained in Example 1, uniformly mixing, adding into a twin-screw extruder for melt extrusion, then drawing, cooling, and pelletizing. The working temperature of the twin-screw extruder was controlled to be 170-220°C, and the vacuum degree was not greater than -0.06 MPa.

[0034] Comparative Example 1

[0035] A polyethylene composite material for a height-adjusting pad plate was prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV aid 3808PP5, 1 part of color master batch PE2718, and 10 parts of unmodified calcium sulfate whisker, uniformly mixing, adding into a twin-screw extruder for melt extrusion, then drawing, cooling, and pelletizing. The working temperature of the twin-screw extruder was controlled to be 170-220°C, and the vacuum degree was not greater than -0.06 MPa.

[0036] Comparative Example 2

[0037] ① 0.2 parts of stearic acid were dispersed in anhydrous ethanol solution, then 9.4 parts of calcium sulfate whisker were added, and stirring was continued at 50-100°C for 2-12 h, then the mixture was filtered and dried to obtain modified calcium sulfate whisker;

[0038] ② 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV aid 3808PP5, 1 part of color master batch PE2718 and 10 parts of modified calcium sulfate whisker obtained in step ① are uniformly mixed, added into a twin-screw extruder for melt extrusion, then drawn, cooled, and pelletized to prepare a polyethylene composite material for height adjustment pad. The working temperature of the twin-screw extruder is controlled at 170-220°C; the vacuum degree is not greater than -0.06 MPa.

[0039] Comparative Example 3:

[0040] ① 0.4 parts of polyacrylic acid is dispersed in deionized water, then 9.4 parts of calcium sulfate whisker is added, stirred at 50-100°C for 2-12h, filtered, the filter cake is washed with anhydrous ethanol, then dispersed in anhydrous ethanol solution, then 0.2 parts of stearic acid in anhydrous ethanol solution is added, and the mixture is continuously stirred at 50-100°C for 2-12h, and finally the mixture is filtered and dried to obtain modified calcium sulfate whisker;

[0041] ② 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV aid 3808PP5, 1 part of color master batch PE2718 and 10 parts of modified calcium sulfate whisker obtained in step ① are uniformly mixed, added into a twin-screw extruder for melt extrusion, then drawn, cooled, and pelletized to prepare a polyethylene composite material for height adjustment pad. The working temperature of the twin-screw extruder is controlled at 170-220°C; the vacuum degree is not greater than -0.06 MPa.

[0042] Comparative Example 4:

[0043] ① 1.2 parts of oxidized polyethylene wax is crushed and dispersed in tetrahydrofuran solution, then 9.4 parts of calcium sulfate whisker is added, stirred at 50-100°C for 2-12h, filtered, the filter cake is dispersed in anhydrous ethanol solution, then 0.2 parts of stearic acid in anhydrous ethanol solution is added, and the mixture is continuously stirred at 50-100°C for 2-12h, and finally the mixture is filtered and dried to obtain modified calcium sulfate whisker;

[0044] The polyethylene composite material for height adjusting pad is prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 5 parts of ethylene-vinyl acetate copolymer, 5 parts of ethylene-octene copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV additive 3808PP5, 1 part of color master batch PE2718 and 10 parts of the modified calcium sulfate whisker obtained in step 1, uniformly mixing, melting and extruding in a double screw extruder, then drawing, cooling and granulating. The working temperature of the double screw extruder is controlled at 170-220°C; the vacuum degree is not more than -0.06 MPa.

[0045] Comparative Example 5

[0046] The polyethylene composite material for height adjusting pad is prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 10 parts of ethylene-vinyl acetate copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV additive 3808PP5, 1 part of color master batch PE2718 and 10 parts of the modified calcium sulfate whisker obtained in step 1, uniformly mixing, melting and extruding in a double screw extruder, then drawing, cooling and granulating. The working temperature of the double screw extruder is controlled at 170-220°C; the vacuum degree is not more than -0.06 MPa.

[0047] Comparative Example 6

[0048] The polyethylene composite material for height adjusting pad is prepared by mixing 68 parts of HDPE resin, 10 parts of HSMPP resin, 10 parts of ethylene-vinyl acetate copolymer, 0.3 parts of lubricant EBS, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.3 parts of anti-UV additive 3808PP5, 1 part of color master batch PE2718 and 10 parts of the modified calcium sulfate whisker obtained in step 1, uniformly mixing, melting and extruding in a double screw extruder, then drawing, cooling and granulating. The working temperature of the double screw extruder is controlled at 170-220°C; the vacuum degree is not more than -0.06 MPa.

[0049] The following test data are the results of body sampling test after the polyethylene composite material for height adjusting pad obtained above is injection molded into height adjusting pad products, as shown in Table 1.

[0050]

[0051]

[0052] As shown in Table 1:

[0053] The mechanical properties and heat resistance of the product of the height adjustment pad obtained by Comparative Example 1 using unmodified calcium sulfate whiskers are obviously lower than those of Examples 1-3; the mechanical properties and heat resistance of the product of the height adjustment pad obtained by Comparative Example 2 using only stearic acid to modify the calcium sulfate whiskers are slightly better than those of Comparative Example 1, but still have a significant gap with the products of Examples 1-3; in Comparative Example 3, polyacrylic acid is used instead of oxidized polyethylene wax, and the rest of the method remains unchanged, and the mechanical properties and heat resistance of the product of the height adjustment pad obtained are not obviously improved compared with Comparative Example 2;

[0054] In Comparative Example 4, the amount of oxidized polyethylene wax is increased in the method of modifying the calcium sulfate whiskers, and the mechanical properties and heat resistance of the product of the height adjustment pad obtained are improved compared with Comparative Examples 1-3, but are still obviously lower than those of Examples 1-3;

[0055] Comparative Examples 5 and 6 are obtained by arbitrarily lacking one of the two toughening agents ethylene-octene copolymer and ethylene-vinyl acetate copolymer, and it can be seen that the combination of ethylene-octene copolymer and ethylene-vinyl acetate copolymer can effectively improve the toughness of the material and the elongation at break of the bulk sample.

[0056] The HDPE composition for the height adjustment pad of the application has the advantages of easy molding processing, high heat resistance, stable shrinkage, and resistance to environmental stress cracking, and is particularly suitable for railway height adjustment pads in a wider range of environments;

[0057] The application obtains a filler that is easy to disperse and has good compatibility with polyethylene and ethylene-vinyl acetate copolymer by surface treatment of calcium sulfate whiskers, and the rigidity of the material can be greatly improved at a lower addition amount to meet various environmental use requirements; the application obtains a height adjustment pad material with a rigid and tough balance, excellent bulk sample performance, and high cost performance by modifying the calcium sulfate whiskers, thereby solving the potential needs of the industry.

[0058] In order to improve the material performance, the application proposes the use of oxidized polyethylene wax in combination with stearic acid on the basis of the current common stearic acid treatment of calcium sulfate whiskers, and the unadsorbed extended polyethylene molecular chain forms molecular chain entanglement or eutectic action with the base polyethylene resin molecular chain while forming adsorption with the calcium sulfate whiskers, thereby greatly improving the force between the whisker and the base resin and further improving the material performance. Only stearic acid cannot achieve the above-mentioned effect.

[0059] The HDPE composition for the height adjustment pad of the application can effectively improve the toughness of the material and the elongation at break of the bulk sample by adding the toughening agent composed of ethylene-octene copolymer and ethylene-vinyl acetate copolymer.

[0060] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be illustrative and is not intended to be limiting to the scope of the present application; the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes such as the different aspects of one or more embodiments of the present application as described above, which are not provided in details for the sake of brevity.

[0061] One or more embodiments of the present application are intended to cover all such alternatives, modifications, and variations as falling within the broad scope of the application. Accordingly, any and all such alternations, modifications, permutations, combinations, enhancements, and the like are intended to fall within the scope of the present application.

Claims

1. A polyethylene composite material for a height adjustment pad, characterized in that: Made from the following components in parts by weight: 55-90 parts of HDPE resin, 0.1-15 parts of HSMPP resin, 1-15 parts of modified calcium sulfate whiskers, 5-15 parts of toughening agent, 0.1-1 part of lubricant, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of anti-UV additive and 0.1-1 parts of masterbatch; The toughening agent is ethylene-octene copolymer and ethylene-vinyl acetate copolymer in a weight ratio of 1:1; The modified calcium sulfate whiskers are made from the following components in parts by weight: 0.6-14.5 parts of calcium sulfate whiskers, 0.1-1 parts of oxidized polyethylene wax, and 0.1-0.5 parts of stearic acid; The preparation method of the modified calcium sulfate whisker comprises the following steps: Weigh calcium sulfate whiskers, oxidized polyethylene wax and stearic acid in parts by weight; First, oxidized polyethylene wax is crushed and dissolved in an organic solvent, then calcium sulfate whiskers are added, heated and stirred for a period of time, and then hot filtered, and the filter cake is dispersed in anhydrous ethanol solution; finally, stearic acid anhydrous ethanol solution is added, heated and stirred, and after the reaction is completed, filtered and dried to obtain modified calcium sulfate whiskers.

2. The polyethylene composite material for height adjustment pad according to claim 1, characterized in that: Made from the following components in parts by weight: 68 parts of HDPE resin, 10 parts of HSMPP resin, 10 parts of modified calcium sulfate whiskers, 10 parts of toughening agent, 0.3 parts of lubricant, 0.4 parts of antioxidant, 0.3 parts of anti-UV additive and 1 part of masterbatch.

3. The polyethylene composite material for height adjustment pad according to claim 2, characterized in that: The modified calcium sulfate whiskers are made from the following components in parts by weight: 9.4 parts of calcium sulfate whiskers, 0.4 parts of oxidized polyethylene wax and 0.2 parts of stearic acid.

4. The polyethylene composite material for height adjustment pad according to claim 1, characterized in that: The antioxidants are antioxidant 1010 and antioxidant 168 in a weight ratio of 1:

1.

5. The polyethylene composite material for height adjustment pad according to claim 1, characterized in that: The anti-UV auxiliary agent is one or more of 3808PP5, UV3346, and UV9900.

6. A method for preparing the polyethylene composite material for height adjustment pads according to any one of claims 1 to 5, characterized in that: The following steps are involved: HDPE resin, HSMPP resin, modified calcium sulfate whisker, toughening agent, lubricant, antioxidant, anti-UV additive and masterbatch are mixed evenly, melt-extruded, then pulled, cooled and pelletized to prepare a polyethylene composite material for height adjustment pads.

7. The method for preparing the polyethylene composite material for height adjustment pad according to claim 6, characterized in that: The melt extrusion step comprises: using a twin-screw extruder, operating at a temperature of 170-220° C., and a vacuum degree of no more than -0.06 MPa.

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