阅读说明：本技术 一种适用于中小管径高速生产的pvc组合物及其制备方法和应用 (PVC composition suitable for medium and small pipe diameter high-speed production and preparation method and application thereof ) 是由 宋科明 李统一 陈国南 郑先伟 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种适用于中小管径高速生产的PVC组合物及其制备方法和应用。本发明的PVC组合物,包括如下组分：PVC,碳酸钙,二氧化钛,钙锌热稳定剂,改性气相二氧化硅,端羟基己二酸季戊四醇酯,高支化度微氧化聚乙烯蜡；所述高支化度微氧化聚乙烯蜡的支化度为50～60甲基数/1000个碳原子,酸值为10～20mgKOH/g；所述改性气相二氧化硅为硅烷偶联剂修饰的气相二氧化硅。通过改性气相二氧化硅、端羟基己二酸季戊四醇酯、高支化度微氧化聚乙烯蜡和钙锌热稳定剂等组分的协同增效作用,有效避免了PVC材料在高速生产的情况下组分析出、过度塑化的问题,使得制得的中小管径PVC管材外观良好,且具有优异的综合性能。(The invention discloses a PVC composition suitable for medium and small pipe diameter high-speed production and a preparation method and application thereof. The PVC composition comprises the following components: PVC, calcium carbonate, titanium dioxide, a calcium-zinc heat stabilizer, modified fumed silica, hydroxyl-terminated pentaerythritol adipate and high-branching-degree micro-oxidized polyethylene wax; the branching degree of the high-branching-degree micro-oxidized polyethylene wax is 50-60 methyl groups/1000 carbon atoms, and the acid value is 10-20 mgKOH/g; the modified fumed silica is fumed silica modified by a silane coupling agent. By the synergistic effect of the components such as the modified fumed silica, the hydroxyl-terminated pentaerythritol adipate, the high-branching-degree micro-oxidized polyethylene wax, the calcium-zinc heat stabilizer and the like, the problems of component separation and excessive plasticization of the PVC material in the high-speed production are effectively solved, so that the prepared PVC pipe with the medium and small pipe diameters is good in appearance and has excellent comprehensive performance.)

1. A PVC composition suitable for medium and small pipe diameter high-speed production is characterized by comprising the following components in parts by weight:

80-100 parts of PVC, 5-30 parts of calcium carbonate, 1-3 parts of titanium dioxide, 5-10 parts of a calcium-zinc heat stabilizer, 0.1-1 part of modified fumed silica, 0.1-1 part of hydroxyl-terminated pentaerythritol adipate and 1-5 parts of high-branching-degree micro-oxidized polyethylene wax;

the branching degree of the high-branching-degree micro-oxidized polyethylene wax is 50-60 methyl groups/1000 carbon atoms, and the acid value is 10-20 mgKOH/g;

the modified fumed silica is fumed silica modified by a silane coupling agent.

2. The PVC composition of claim 1, wherein the highly branched micro-oxidized polyethylene wax has a viscosity of 5 to 10Pa.S @150 ℃.

3. The PVC composition of claim 1, wherein the mass ratio of the calcium-zinc heat stabilizer to the modified fumed silica to the hydroxyl-terminated pentaerythritol adipate to the highly branched micro-oxidized polyethylene wax is 10: 0.5-1: 2-4.

4. The PVC composition according to claim 1, wherein the hydroxyl-terminated pentaerythritol adipate has an acid value of 0.5mgKOH/g or less and a hydroxyl value of 70 to 90 mgKOH/g.

5. The PVC composition according to claim 1, wherein the density of silanol groups on the surface of the modified fumed silica is 3 to 5SiOH/nm²。

6. The PVC composition of claim 1, further comprising 0.5 to 2 parts by weight of a processing aid and 5 to 10 parts by weight of an impact modifier.

7. A process for the preparation of a PVC composition according to any of claims 1 to 5, comprising the steps of:

PVC, calcium carbonate, titanium dioxide, a calcium-zinc heat stabilizer, modified fumed silica, hydroxyl-terminated pentaerythritol adipate and high-branching-degree micro-oxidized polyethylene wax are mixed and then added into an extruder, and the PVC composition is obtained through melt blending, extrusion and granulation.

8. A medium and small-diameter PVC pipe is characterized by being prepared from the PVC composition as claimed in any one of claims 1 to 6, and the diameter of the medium and small-diameter PVC pipe is less than or equal to 200 mm.

9. A method for preparing the PVC pipe with the medium and small pipe diameter as recited in claim 8, which comprises the following steps:

the PVC composition as defined in any one of claims 1 to 6 is added into a conical counter-rotating twin-screw extruder, and the medium and small-diameter PVC pipes are obtained after melt plasticizing, extrusion, cooling forming and fixed-length cutting.

10. The preparation method of the special-shaped high-strength high.

Technical Field

The invention relates to the technical field of PVC heat stabilizers, in particular to a PVC composition suitable for medium and small pipe diameter high-speed production and a preparation method and application thereof.

Background

The PVC pipeline has the advantages of excellent flame retardance, wear resistance, chemical corrosion resistance, mechanical property, electrical insulation and the like, and is widely applied to the fields of industry, building, municipal administration, agriculture and the like. The bond energy of tertiary chlorine and tertiary hydrogen structures in PVC molecular chains is low, HCl is very easy to remove to generate free radicals, and PVC is O-doped₂Can degrade and age under the conditions of high temperature and illumination; in addition, the decomposition temperature of the PVC resin is about 130 ℃, but the molding temperature of the PVC resin is 180 ℃ or higher, and thus, in order to realize the processability of the PVC resin, a thermal stabilizer needs to be added to the PVC material system.

Generally, PVC pipelines with the pipe diameter of less than 200mm can be called medium and small-diameter PVC pipelines, and the maximum speed of industrial production line of the medium and small-diameter PVC pipelines can only reach 6-8 m/min. In order to ensure the production efficiency and obtain higher productivity, a production mode of extruding from multiple cavities of a neck mold can be adopted to improve the production line speed. However, due to the complex structure of the mould and the overhigh pressure in the mould at a higher production line speed, the excessive plasticization of the PVC melt is easily caused, and the comprehensive performance of the PVC pipe is further reduced. At the same time, the high melt pressure in the mold also aggravates the precipitation of the heat stabilizer.

Chinese patent application CN 112940412 a discloses a calcium zinc stabilizer for high speed extruded PVC-U drainage pipe, comprising zinc stearate, calcium stearate, zeolite, antioxidant, synergistic thermal stabilizer, high-end lubricant, polyol and specific metal saponification compound. However, this prior art does not disclose specific kinds of synergistic heat stabilizers, high-end lubricants and specific metal soap compounds, nor does it disclose specific values of the production line speed thereof. Chinese patent application CN103570973A discloses a high-speed extruded calcium-zinc composite stabilizer, which comprises components such as polycarboxylic acid polyol ester, zinc stearate, calcium stearate, hydrotalcite, 4A zeolite, an internal lubricant, an external lubricant and the like, and the production line speed equivalent to that of composite lead salt is obtained. However, the components contain a large amount of hydrotalcite and 4A zeolite, and the unmodified inorganic matters have poor compatibility with PVC and are easy to precipitate. In addition, the production line speed can only reach the level equivalent to that of the composite lead salt, and the risk of overhigh plasticizing degree in the multi-cavity film extrusion process cannot be solved.

Therefore, it is necessary to develop a PVC composition suitable for high-speed production of medium and small pipe diameters.

Disclosure of Invention

The invention aims to overcome the defects of excessive plasticization of a PVC melt and precipitation of a heat stabilizer during high-speed production in the prior art, provides a PVC composition suitable for high-speed production of medium and small pipe diameters, and can keep reasonable plasticization degree at a production line speed of 14-16 m/min without precipitation of the heat stabilizer.

Another object of the present invention is to provide a process for the preparation of the above PVC composition.

The invention also aims to provide the application of the PVC composition in preparing medium and small-diameter PVC pipes.

In order to solve the technical problems, the invention adopts the technical scheme that:

a PVC composition suitable for medium and small pipe diameter high-speed production comprises the following components in parts by weight:

80-100 parts of PVC (polyvinyl chloride),

5-30 parts of calcium carbonate,

1-3 parts of titanium dioxide,

5-10 parts of a calcium-zinc heat stabilizer,

0.1 to 1 part of modified fumed silica,

0.1 to 1 part of hydroxyl-terminated pentaerythritol adipate,

1-5 parts of high-branching-degree micro-oxidized polyethylene wax;

the branching degree of the high-branching-degree micro-oxidized polyethylene wax is 50-60 methyl groups/1000 carbon atoms, and the acid value is 10-20 mgKOH/g;

the modified fumed silica is fumed silica modified by a silane coupling agent.

Under the combined action of the modified fumed silica, the hydroxyl-terminated pentaerythritol adipate and the high-branching-degree micro-oxidized polyethylene wax, the PVC composition can keep no precipitation or low precipitation under the condition of high-speed production, the excessive plasticization of high melt pressure to a PVC melt in the processing process is reduced, and the prepared PVC composition has good comprehensive performance.

The hydroxyl-terminated pentaerythritol adipate has good compatibility with PVC, and the existence of the hydroxyl-terminated group enables oxygen atoms in the hydroxyl groups to promote zinc chloride generated by complexing zinc salt in the calcium-zinc heat stabilizer, so that the synergistic effect of the calcium-zinc heat stabilizer on the heat stability of PVC is further improved. The silane coupling agent modified fumed silica has higher surface polarity, can quickly adsorb HCl degraded and removed by PVC, and is not easy to desorb, so that the autocatalytic degradation of PVC molecules by HCl is blocked.

However, the inventor researches and discovers that for medium and small-diameter PVC pipes produced at high speed, the problem of improving the precipitation or degradation of a system only by modified fumed silica and hydroxyl-terminated pentaerythritol adipate is still far insufficient, and the components in the PVC composition are still degraded and precipitated under high-melt pressure. The high-branching-degree micro-oxidized polyethylene wax has more branched chains in a molecular structure due to high branching degree, has excellent internal and external lubricating effect due to micro-oxidation treatment on the branched chains, has better compatibility among various components, reduces component precipitation, ensures that a PVC matrix has better fluidity among processing dies, and avoids excessive plasticization under high melt pressure.

The branching degree of the highly branched micro-oxidized polyethylene wax is expressed by the number of methyl groups contained in each 1000 carbon atoms. The number of methyl groups represents the number of branched chains in the molecular chain of the highly branched micro-oxidized polyethylene wax, and the higher the number of methyl groups is, the higher the branching degree of the highly branched micro-oxidized polyethylene wax is.

The acid value of the high-branching-degree micro-oxidized polyethylene wax can reflect the oxidation degree of the high-branching-degree micro-oxidized polyethylene wax. A higher acid number indicates a higher degree of oxidation of the polyethylene wax and a higher polarity. Under the acid value of 10-20 mgKOH/g, the high-branching-degree polyethylene wax has micro-oxidation degree and proper polarity.

Preferably, the viscosity of the high-branching-degree micro-oxidized polyethylene wax is 5-10 Pa.S @150 ℃.

Preferably, the mass ratio of the calcium-zinc heat stabilizer, the modified fumed silica, the hydroxyl-terminated pentaerythritol adipate and the high-branching-degree micro-oxidized polyethylene wax is 10: 0.5-1: 2-4.

Within the above mass range, the overall performance of the PVC composition is superior.

Preferably, the acid value of the hydroxyl-terminated pentaerythritol adipate is less than or equal to 0.5mgKOH/g, and the hydroxyl value is 70-90 mgKOH/g.

Preferably, the preparation method of the modified fumed silica comprises the following steps:

dispersing the fumed silica and a silane coupling agent in an organic solvent, carrying out reflux reaction for 2-4 h at the temperature of 60-80 ℃, and carrying out post-treatment to obtain the modified fumed silica.

Preferably, the mass ratio of the fumed silica to the silane coupling agent is (40-50): (20-30).

Preferably, the organic solvent is one or more of acetone, methanol, ethanol and ethyl acetate.

Preferably, the silane coupling agent is one or more of KH570, KH560 and KH 171.

Preferably, the density of silanol groups on the surface of the modified fumed silica is 3-5 SiOH/nm²。

Preferably, the specific surface area of the modified fumed silica is 250-350 m²/g。

The calcium-zinc heat stabilizer is a mixture of calcium stearate and zinc stearate.

Preferably, the mass ratio of the calcium stearate salt to the zinc stearate salt is (15-30) to (10-20).

Preferably, the PVC composition can also comprise 0.5-2 parts by weight of processing aid and 5-10 parts by weight of impact modifier.

Optionally, the impact modifier is Chlorinated Polyethylene (CPE) and/or methyl methacrylate-butadiene-styrene terpolymer (MBS).

Optionally, the processing aid is an acrylate copolymer.

The processing aid can promote the plasticizing effect of the PVC-U material to be better.

The invention also provides a preparation method of the PVC composition suitable for medium and small pipe diameter high-speed production, which comprises the following steps:

mixing PVC, calcium carbonate, titanium dioxide, a calcium-zinc heat stabilizer, modified fumed silica, hydroxyl-terminated pentaerythritol adipate, high-branching-degree micro-oxidized polyethylene wax, an impact modifier (if any) and a processing aid (if any), adding the mixture into an extruder, and carrying out melt blending and extrusion granulation to obtain the PVC composition.

The invention also discloses a medium and small-diameter PVC pipe which is prepared from the PVC composition, wherein the pipe diameter of the medium and small-diameter PVC pipe is less than or equal to 200 mm.

The invention also provides a preparation method of the medium and small-diameter PVC pipe, which comprises the following steps:

and adding the PVC composition into a conical counter-rotating double-screw extruder, and performing melt plasticization, extrusion, cooling forming and fixed-length cutting to obtain the medium and small-diameter PVC pipe.

Preferably, the neck mold of the conical counter-rotating twin-screw extruder is four-cavity extrusion, and the production line speed is 14-16 m/min.

Compared with the prior art, the invention has the beneficial effects that:

the invention develops a PVC composition suitable for medium and small pipe diameter high-speed production, and the synergistic interaction of other components such as modified fumed silica, hydroxyl-terminated pentaerythritol adipate, high-branching-degree micro-oxidized polyethylene wax, calcium-zinc heat stabilizer and the like effectively avoids the problems of component precipitation and excessive plasticization of a PVC material under the condition of high-speed production, so that the prepared medium and small pipe diameter PVC pipe has good appearance and excellent comprehensive performance.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The starting materials in the examples and comparative examples are all commercially available, wherein:

the calcium-zinc heat stabilizer is purchased from Jinchang tree new material science and technology Co., Ltd, JCS-208;

the modified fumed silica is prepared by the following method:

dispersing the fumed silica and a silane coupling agent KH570 in acetone according to the mass ratio of 45:25, carrying out reflux heating reaction at the reaction temperature of 70 ℃ for 2h, separating and drying to obtain the modified fumed silica, wherein the density of silanol groups is 4.1SiOH/nm²(ii) a The specific surface area of the modified fumed silica is 302m²/g；

The hydroxyl-terminated pentaerythritol adipate is prepared by the following method:

under the action of a concentrated sulfuric acid catalyst, adding hydroxyl-terminated adipic acid and pentaerythritol into a round-bottom flask with a stirring device according to a molar ratio of 1:2, and carrying out esterification reaction under a vacuum condition, wherein the esterification reaction temperature is 150 ℃, and the reaction time is 4 hours, so as to obtain hydroxyl-terminated pentaerythritol adipate, the acid value of which is 0.2mgKOH/g, and the hydroxyl value of which is 90 mgKOH/g;

the high-branching-degree micro-oxidized polyethylene wax A is purchased from Honeywell, the branching degree of the polyethylene wax A is 55 (methyl number/1000 carbon atoms), the acid value is 16mgKOH/g, and the viscosity is 8.5Pa.S @150 ℃;

the high-branching-degree micro-oxidized polyethylene wax B is purchased from Honeywell, the branching degree of the polyethylene wax B is 50 (number of methyl groups/1000 carbon atoms), the acid value is 10mgKOH/g, and the viscosity is 9.8Pa.S @150 ℃;

the high-branching-degree micro-oxidized polyethylene wax C is purchased from Honeywell, the branching degree of the polyethylene wax C is 60 (methyl number/1000 carbon atoms), the acid value is 20mgKOH/g, and the viscosity is 5Pa.S @150 ℃;

the high-branching-degree micro-oxidized polyethylene wax D is purchased from Shanxi' an, has the branching degree of 50 (number of methyl groups/1000 carbon atoms), the acid value of 12mgKOH/g and the viscosity of 7.5Pa.S @150 ℃;

oxidized polyethylene wax E is purchased from the Huanfeng chemical industry, the branching degree of the oxidized polyethylene wax E is 20 (the number of methyl groups/1000 carbon atoms), the acid value is 50mgKOH/g, and the viscosity is 2.5Pa.S @150 ℃;

oxidized polyethylene wax F is purchased from the self-circulation chemical industry, the branching degree of the oxidized polyethylene wax F is 14 (the number of methyl groups/1000 carbon atoms), the acid value is 6mgKOH/g, and the viscosity is 13Pa.S @150 ℃;

the composite lead salt is purchased from Hebei Jingxin chemical Co.

Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Examples 1 to 13

Embodiments 1 to 13 respectively provide a PVC composition and a PVC pipe prepared therefrom, the content of each component is as shown in table 1, and the preparation method of the PVC composition comprises:

uniformly mixing the components according to the table 1, adding the mixture into a double-screw extruder, and carrying out melt blending and extrusion granulation to obtain a PVC composition;

the preparation method of the PVC pipe comprises the following steps:

adding the PVC composition into a conical counter-rotating double-screw extruder, extruding the PVC composition through a die with four cavities at the production line speed of 16m/min, and performing melting plasticization, extrusion, molding and cutting to obtain the PVC pipe with the pipe diameter of 20 mm.

TABLE 1 component content (parts by weight) of PVC compositions of examples 1 to 13

Comparative examples 1 to 6

Comparative examples 1 to 6 respectively provide a PVC composition and a prepared PVC pipe, the contents of the components are shown in Table 2, and the preparation method of the PVC composition comprises the following steps:

uniformly mixing the components according to the table 2, adding the mixture into a double-screw extruder, and carrying out melt blending and extrusion granulation to obtain a PVC composition;

the preparation method of the PVC pipe comprises the following steps:

adding the PVC composition into a conical counter-rotating double-screw extruder, extruding the PVC composition through a die with four cavities at the production line speed of 16m/min, and extruding, molding and cutting to obtain the PVC pipe with the pipe diameter of 20 mm.

TABLE 2 component content (parts by weight) of PVC compositions of comparative examples 1 to 6

Performance testing

The PVC compositions and PVC pipes prepared in the above examples and comparative examples are subjected to performance tests, and the test methods are as follows:

precipitation conditions: and (3) carrying out a pipe extrusion experiment on the PVC composition by using an extruder with a four-cavity neck mold, wherein the extrusion speed is 16m/min, observing precipitates at the neck mold after 4 hours of continuous startup, and weighing the mass of the precipitates, wherein less than 1mg is I grade, 1-5 mg is II grade, and more than 5mg is III grade.

Degree of plasticization: according to the requirements of ISO 18373, taking the tube wall core layer at 0 °, 90 °, 180 ° and 270 ° of the tube circumference, respectively, and taking the average value after testing by using DSC.

The test results of the above examples and comparative examples are shown in tables 3 and 4.

TABLE 3 test results of examples 1 to 13

TABLE 4 test results for comparative examples 1 to 6

According to the test results in table 3, the PVC compositions prepared in the examples of the present invention have no precipitation when extruded at a high speed by an extruder with a die having four cavities, and have a plasticization degree of 72.76-76.22%, which indicates a high plasticization degree and good uniformity.

According to the test results in the table 4, according to the comparative examples 1 to 3, when the PVC composition does not contain modified fumed silica, hydroxyl-terminated pentaerythritol adipate or high-branching-degree micro-oxidized polyethylene wax, precipitation occurs to different degrees in the high-speed extrusion process, the plasticization degree reaches more than 85%, and experiments show that when the plasticization degree of PVC reaches more than 85%, PVC molecular chains are degraded due to excessive plasticization, and the mechanical property of the product is reduced.

Compared with the comparative example 4 and the comparative example 5, under the condition that the acid value of the high-branching-degree micro-oxidized polyethylene wax is too high or too low and the branching degree is too low, 1-5 mg of precipitates exist in the PVC composition in the high-speed extrusion process, and the requirement of no precipitation cannot be met. As can be seen from comparative example 7, when the composite lead salt is used as the stabilizer, precipitation exists to a certain extent under the condition of multi-cavity high-speed production, and the PVC material is excessively plasticized, so that the PVC composition has better comprehensive performance under the condition of high-speed production.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.