阅读说明：本技术 一种高熔体强度聚丙烯及其制备方法 (High-melt-strength polypropylene and preparation method thereof ) 是由 李应平 苏艳敏 李欣 王小宪 于 2019-11-22 设计创作，主要内容包括：本发明公开了一种高熔体强度聚丙烯及其制备方法,包括质量比的原料：聚丙烯树脂100份；含双键线性聚合物5-30份；金属化合物1-5份；引发剂0.1-0.5份；自由基稳定剂0.1-0.5份；抗氧剂0.1-0.5份。本发明通过原料的预交联、预分散、反应接枝工艺得到离子交联型高熔体强度聚丙烯。本发明提供了一种具有优异的熔体强度、熔体指数和拉伸强度指标的高熔体强度聚丙烯,并提供一种工艺简单、兼具良好加工性能和力学性能的高熔体强度聚丙烯的方法,本发明能在保持聚丙烯原有力学性能和加工流动性的基础上,实现聚丙烯熔体强度的大幅提高。(The invention discloses a high melt strength polypropylene and a preparation method thereof, wherein the high melt strength polypropylene comprises the following raw materials in percentage by mass: 100 parts of polypropylene resin; 5-30 parts of a double-bond-containing linear polymer; 1-5 parts of a metal compound; 0.1-0.5 part of initiator; 0.1-0.5 part of free radical stabilizer; 0.1-0.5 part of antioxidant. The invention obtains the ionic crosslinking type high-melt-strength polypropylene by the processes of pre-crosslinking, pre-dispersing and reactive grafting of raw materials. The invention provides the high melt strength polypropylene with excellent melt strength, melt index and tensile strength indexes, and provides the method for preparing the high melt strength polypropylene with simple process and good processability and mechanical property.)

1. The high melt strength polypropylene is characterized by comprising the following raw materials in percentage by mass:

2. the polypropylene as claimed in claim 1, wherein the polypropylene resin is homo-, block-and random-polypropylene having a weight-average molecular weight of 50000-250000 g/mol.

3. The high melt strength polypropylene according to claim 1, wherein the double bond-containing linear polymer is an unsaturated fatty acid or an unsaturated polyester having a carboxyl group at one or both ends;

the unsaturated fatty acid is tetradecenoic acid, octadecenoic acid, docosenoic acid, tetracosenoic acid, octadecadienoic acid, eicosadienoic acid or arachidonic acid;

the unsaturated polyester is 191#, 192#, 196#, 189# or 199# unsaturated polyester.

4. A high melt strength polypropylene according to claim 1 wherein said metal compound is a metal oxide or metal hydroxide;

the metal oxide is ZnO, CuO, MgO, BaO, Al₂O₃、Fe₂O₃、SnO、CaO、TiO₂Or ZrO₂；

The hydroxide is LiOH, NaOH, KOH, Cu (OH)₂、Cu₂O(OH)₂、Mg(OH)₂、Mg₂O(OH)₂、Ba(OH)₂、Zn(OH)₂、Sn(OH)₂Or Ca (OH)₂。

5. A high melt strength polypropylene according to claim 1 wherein the initiator is azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, diisophenylpropyl peroxide, lauroyl peroxide, cumene hydroperoxide, diisophenyl peroxydicarbonate, dicycloethyl peroxydicarbonate, di-t-butyl peroxide, t-butyl hydroperoxide, n-butyl di-t-butylperoxyvalerate or di-t-butyl peroxide.

6. A high melt strength polypropylene according to claim 1 wherein the free radical stabilizer is tetramethylthiuram disulfide or zinc dimethyldithiocarbamate.

7. The high melt strength polypropylene according to claim 1, wherein the antioxidant is a phenolic antioxidant, an aminic antioxidant or a complex antioxidant;

the phenolic antioxidant is irganox1010, BHT, irganox565, irganox1076, irganox245, antioxidant BB10, antioxidant2246, nocrac300, goodrite3114 or goodrite 3125;

the amine antioxidant is KY401, 4010NA, 4020 or 4030 antioxidant;

the compound antioxidant is B215, B225 or B900.

8. A process for producing a high melt strength polypropylene according to any one of claims 1 to 7, comprising the steps of:

1) pre-crosslinking:

uniformly mixing 30-50% of each substance in 100 parts of polypropylene resin, 5-30 parts of double-bond linear polymer, 0.1-0.5 part of initiator, 0.1-0.5 part of free radical stabilizer and 0.1-0.5 part of antioxidant according to the mass ratio, adding the mixture into a single-screw extruder or a double-screw extruder, and extruding and granulating to obtain pre-crosslinked polypropylene;

2) pre-dispersing:

uniformly mixing the rest 100 parts of polypropylene with the amount of 50-70% and 1-5 parts of metal compound, adding the mixture into a screw extruder, and extruding and granulating to obtain pre-dispersed polypropylene containing the metal compound;

3) reaction grafting:

and (3) uniformly mixing the pre-crosslinked polypropylene and the pre-dispersed polypropylene obtained in the step with the remaining 50-70% of the double-bond linear polymer, the initiator, the free radical stabilizer and the antioxidant, adding the mixture into a screw extruder, and extruding and granulating to obtain the ionic crosslinking type high-melt-strength polypropylene.

9. The method as claimed in claim 8, wherein the screw extruder is a single screw extruder or a twin screw extruder, the rotation speed of the single screw extruder is 60-150r/min, the rotation speed of the twin screw extruder is 60-400r/min, the temperature of the feeding section of the single screw extruder or the twin screw extruder is 160-190 ℃, and the temperature from the melting section to the neck mold is 180-260 ℃.

10. The method as claimed in claim 8, wherein the melt strength of the ionomer polypropylene is increased to 180% -470% of the raw material, the melt index is 86% -130% of the raw material, and the tensile strength is 102% -129% of the raw material.

Technical Field

The invention relates to the field of high-performance modification of high polymer materials, in particular to a preparation method of high-melt-strength polypropylene for foaming.

Background

Polypropylene (PP) is one of the resins which are most widely applied and have the fastest yield increase in the world at present, and has the characteristics of low density, no toxicity, easiness in processing and forming, excellent product comprehensive performance and the like. In particular, the polypropylene has unique tensile property, degradation property and excellent heat resistance, so that the polypropylene has huge market and application prospects in the fields of extrusion foaming, thermoforming, extrusion coating, blown film and the like. However, the existing common polypropylene is of a linear structure, when the temperature is raised to the melting temperature, the melt elasticity of the polypropylene is rapidly reduced, and in the molten state, the linear structure polypropylene has no strain hardening effect, the lower melt strength cannot ensure the tensile stress borne by the cell wall in the process of growing the bubbles, so that the bubbles collapse and break, the processing window of the polypropylene is very narrow, the foaming temperature suitable for the general polypropylene is only 4-6 ℃, and the aperture ratio of the foamed product is very high, so that the use requirement cannot be met. Thus, high melt strength polypropylene materials are first required to produce expanded polypropylene. In terms of molecular structure, the melt strength of PP can be improved by three methods, namely increasing molecular weight, improving molecular weight distribution, introducing long-chain branched chains on PP molecular chains and the like.

At present, three methods are mainly used for improving the melt strength of PP: (1) the method is a reactor method, the method carries out grafting reaction in the polymerization process or the later polymerization stage of PP to directly synthesize the PP containing the long branched chain, the PP with high melt strength prepared by the method has both melt strength and processability, but the method has high preparation difficulty and large investment, and only countries such as Belgium and the like have the technology at present; (2) non-reactive blending modification, such as blending PP with LLDPE, ultra-high molecular weight polyethylene or elastomer with high melt strength, the method improves the melt strength of PP, but the heat resistance and degradation performance are also obviously reduced; (3) the post-reactor method introduces a branched structure on the common linear PP by means of ray irradiation, reactive extrusion and the like, and the reactive extrusion method in the post-reactor method is widely researched for preparing the high melt strength polypropylene at present.

The high-energy irradiation method is to make PP molecular chain generate free radical by high-energy ray, then graft with PP molecular chain or added grafting monomer, to improve the melt strength of PP. The disadvantage of the irradiation grafting method is that the equipment investment is large, and the modification efficiency of polypropylene is low. The reactive extrusion method is to put PP into a screw, initiate the grafting reaction of PP itself or with a grafting monomer by in-situ thermal initiation or addition of a radical initiator, and further add a radical stabilizer or an auxiliary grafting monomer, such as styrene or multifunctional acrylates, in order to prevent the degradation of PP in the grafting process and improve the grafting rate.

When the conventional reaction extrusion method is used for preparing the high-melt-strength polypropylene, a multifunctional group micromolecule grafting monomer needs to be added, a long-chain grafted polypropylene structure is not easy to form, the effect of improving the melt strength of the polypropylene is limited, the problem of insufficient grafting and overhigh crosslinking is easy to occur, and the processing performance is influenced. In order to overcome the problem, researchers graft long-chain grafted polypropylene on a polypropylene molecular chain by grafting long-chain molecules containing double bonds such as unsaturated polyester and the like through an initiator so as to form a long-chain branched structure, so that the long-chain grafted polypropylene has good processing flowability, but the introduction of the long-chain molecules easily causes the reduction of the mechanical property of the material.

From the above discussion, how to improve the melt strength of polypropylene without sacrificing the mechanical properties and processing flowability of polypropylene is the key for preparing high melt strength polypropylene by reactive extrusion method, and the related patents of reactive extrusion method at present rarely can achieve this goal.

Disclosure of Invention

The invention provides the high melt strength polypropylene with excellent melt strength, melt index and tensile strength indexes, and provides the method for preparing the high melt strength polypropylene with good processability and mechanical property, which aims to solve the problem of excessive reduction of mechanical property in the preparation of the high melt strength polypropylene.

The polypropylene prepared by the method has high melt strength of reversible ionic crosslinking long-chain grafting.

The invention is realized by the following technical scheme.

The invention provides high melt strength polypropylene, which comprises the following raw materials in percentage by mass:

preferably, the polypropylene resin is homopolymerized, blocked and random polypropylene, and the weight-average molecular weight is 50000-250000 g/mol.

Preferably, the double bond-containing linear polymer is unsaturated fatty acid or unsaturated polyester, one end or two ends of which are carboxyl groups;

the unsaturated fatty acid is tetradecenoic acid (myristoleic acid), octadecenoic acid (oleic acid), docosenoic acid (erucic acid), tetracosenoic acid (nervonic acid), octadecadienoic acid (linoleic acid), eicosadienoic acid (aconitic acid), and arachidonic acid (arachidonic acid);

the unsaturated polyester is 191#, 192#, 196#, 189# or 199# unsaturated polyester.

Preferably, the metal compound is a metal oxide or a metal hydroxide;

the metal oxide is ZnO, CuO, MgO, BaO, Al₂O₃、Fe₂O₃、SnO、CaO、TiO₂Or ZrO₂；

The hydroxide is LiOH, NaOH, KOH, Cu (OH)₂、Cu₂O(OH)₂、Mg(OH)₂、Mg₂O(OH)₂、Ba(OH)₂、Zn(OH)₂、Sn(OH)₂Or Ca (OH)₂。

Preferably, the initiator is azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, diisophenylpropyl peroxide, lauroyl peroxide, cumene hydroperoxide, diisophenyl peroxydicarbonate, dicycloethyl peroxydicarbonate, di-t-butyl peroxide, t-butyl hydroperoxide, n-butyl di-t-butylperoxyvalerate or di-t-butyl peroxide.

Preferably, the free radical stabilizer is tetramethylthiuram disulfide or zinc dimethyldithiocarbamate.

Preferably, the antioxidant is a phenolic antioxidant, an amine antioxidant or a composite antioxidant;

the phenolic antioxidant is irganox1010, BHT, irganox565, irganox1076, irganox245, antioxidant BB10, antioxidant2246, nocrac300, goodrite3114 or goodrite 3125;

the amine antioxidant is KY401, 4010NA, 4020 or 4030 antioxidant;

the compound antioxidant is B215, B225 or B900.

The invention correspondingly provides a preparation method of the high melt strength polypropylene, which comprises the following steps:

1) pre-crosslinking:

uniformly mixing 30-50% of each substance in 100 parts of polypropylene resin, 5-30 parts of double-bond linear polymer, 0.1-0.5 part of initiator, 0.1-0.5 part of free radical stabilizer and 0.1-0.5 part of antioxidant according to the mass ratio, adding the mixture into a single-screw extruder or a double-screw extruder, and extruding and granulating to obtain pre-crosslinked polypropylene;

2) pre-dispersing:

uniformly mixing the rest 100 parts of polypropylene with the amount of 50-70% and 1-5 parts of metal compound, adding the mixture into a screw extruder, and extruding and granulating to obtain pre-dispersed polypropylene containing the metal compound;

3) reaction grafting:

and (3) uniformly mixing the pre-crosslinked polypropylene and the pre-dispersed polypropylene obtained in the step with the remaining 50-70% of the double-bond linear polymer, the initiator, the free radical stabilizer and the antioxidant, adding the mixture into a single-screw extruder or a double-screw extruder, and extruding and granulating to obtain the ionic crosslinking type high-melt-strength polypropylene.

Further, the screw extruder is a single screw extruder or a double screw extruder, the rotating speed of the single screw extruder is 60-150r/min, the rotating speed of the double screw extruder is 60-400r/min, the temperature of the feeding section of the single screw extruder or the double screw extruder is 160-190 ℃, and the temperature from the melting section to the neck mold is 180-260 ℃.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

the invention can greatly improve the melt strength of the polypropylene on the basis of keeping the original mechanical property and processing fluidity of the polypropylene.

1) The invention adopts the linear polymer containing double bonds as the graft of the polypropylene, can lead the polypropylene to form a long-chain branched structure and improve the melt strength of the grafted polypropylene. The linear polymer contains carboxylic acid end groups, can form a reversible ionic crosslinking structure with added metal ions, is not crosslinked at high temperature, does not influence the processing performance of the polypropylene, is crosslinked at low temperature, is beneficial to improving the mechanical performance under the use condition, and partially offsets the reduction of the mechanical performance caused by the introduction of the linear polymer.

2) The invention adopts the metal compound to carry out ionic bond combination with carboxylic acid groups, so that ionic crosslinking is generated between the grafted polypropylene, the mechanical property of the product is improved, and the reduction of the mechanical property of the grafted polypropylene caused by the introduction of linear polymers is compensated. The metal compound has an average particle diameter of less than 0.1. mu.m, and the use of a metal compound having an excessively large average particle diameter is disadvantageous in the generation of an ionomer structure.

3) The initiator adopted by the invention is mainly used for generating free radicals through self-cracking, so that the polypropylene molecular chain is dehydrogenated to generate free radicals, or the double-bond linear polymer generates free radicals, thereby initiating grafting and crosslinking reactions.

4) The free radical stabilizer adopted by the invention is mainly used for inhibiting the degradation of polypropylene.

Because the compatibility of the linear polymer and the polypropylene is greatly different, the grafted polypropylene of the linear polymer obtained in the pre-crosslinking step can be used as a compatilizer in the subsequent reaction grafting step, and the grafting efficiency of the linear polymer is improved.

Under the condition of the same raw material, the melt strength of the ionic crosslinking type high-melt-strength polypropylene prepared by the invention is improved to 180-470% of the raw material, the melt index is 86-130% of the raw material, and the tensile strength is 102-129% of the raw material.

Detailed Description

The present invention will be described in detail with reference to specific embodiments, which are illustrative of the invention and are not to be construed as limiting the invention.

The invention discloses a preparation process of high melt strength polypropylene, which comprises three steps of pre-crosslinking, pre-dispersing and reactive grafting, and comprises the following specific steps:

the polypropylene resin is usually homo-, block-and random-polypropylene, and has a weight-average molecular weight of 50000-250000g/mol, preferably 100000-150000 g/mol.

Wherein the double bond-containing linear polymer is unsaturated polyester or unsaturated fatty acid with carboxyl at one or two ends, and the unsaturated fatty acid is tetradecenoic acid (myristoleic acid), octadecenoic acid (oleic acid), docosenoic acid (erucic acid), tetracosenoic acid (nervonic acid), octadecadienoic acid (linoleic acid), eicosadienoic acid (aconitic acid), and arachidonic acid (arachidonic acid), preferably octadecenoic acid, docosenoic acid, tetracosenoic acid, octadecadienoic acid, and eicosadienoic acid; the unsaturated polyester is mainly commercial products, such as 191#, 192#, 196#, 189#, 199# unsaturated polyester, and 191#, 192# unsaturated polyester are preferred.

Among them, a metal oxide or a metal hydroxide may be used as the metal compound constituting the specific metal compound particles. Specific examples of the metal oxide constituting the specific metal compound particle include ZnO, CuO, MgO, BaO and Al₂O₃、Fe₂O₃、SnO、CaO、TiO₂Or ZrO₂Etc., among which ZnO; specific examples of the hydroxide include LiOH, NaOH, KOH, Cu (OH)₂、Cu₂O(OH)₂、Mg(OH)₂、Mg₂O(OH)₂、Ba(OH)₂、Zn(OH)₂、Sn(OH)₂Or Ca (OH)₂Etc., wherein Mg (OH) is preferred₂、Mg₂O(OH)₂Or Zn (OH)₂。

The initiator includes azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, diisophenylpropyl peroxide, lauroyl peroxide, cumene hydroperoxide, diisophenyl peroxydicarbonate, dicycloethyl peroxydicarbonate, di-t-butyl peroxide, t-butyl hydroperoxide, n-butyl di-t-butylperoxyvalerate, di-t-butyl peroxide, etc., and of these, diisophenylpropyl peroxide is preferable.

Wherein the free radical stabilizer can be tetramethylthiuram disulfide or zinc dimethyldithiocarbamate.

Wherein, the antioxidant is a conventional plastic antioxidant: such as a phenolic antioxidant, an aminic antioxidant or a complex antioxidant, said phenolic antioxidant being irganox1010, BHT, irganox565, irganox1076, irganox245, antioxidant BB10, antioxidant2246, nocrac300, goodrite3114 or goodrite 3125; the amine antioxidant is KY401, 4010NA, 4020 or 4030 antioxidant; the compound antioxidant is B215, B225 or B900.

The preparation method of the high melt strength polypropylene comprises the following specific steps:

1) pre-crosslinking step: uniformly mixing 30-50% of PP (polypropylene) in percentage by mass with the double-bond linear polymer, the initiator, the free radical stabilizer and the antioxidant in corresponding proportion, adding the mixture into a single-screw extruder or a double-screw extruder, wherein the rotating speed of the single-screw extruder is 60-150r/min, the rotating speed of the double-screw extruder is 60-400r/min, the temperature of a feeding section of the single-screw extruder or the double-screw extruder is 160-190 ℃, the temperature from a melting section to a neck mold is 180-260 ℃, and extruding and granulating to obtain the pre-crosslinked polypropylene.

2) Pre-dispersing: uniformly mixing the remaining 50-70% of the polypropylene in the step 1) and all the metal compounds, adding the mixture into a single-screw extruder or a double-screw extruder, wherein the rotating speed of the single-screw extruder is 60-150r/min, the rotating speed of the double-screw extruder is 60-400r/min, the temperature of a feeding section of the single-screw extruder or the double-screw extruder is 160-190 ℃, the temperature from a melting section to a neck mold is 180-260 ℃, and extruding and granulating to obtain the pre-dispersed polypropylene containing the metal compounds. The pre-dispersion step pre-disperses the metal compound in part of the polypropylene, and the subsequent reaction grafting step re-disperses the metal compound, so that the dispersion of the metal compound in the polypropylene is improved, and the ionic crosslinking efficiency is improved.

3) A reaction grafting step: uniformly mixing the pre-crosslinked polypropylene and the pre-dispersed polypropylene obtained in the step with the rest 50-70% of the double-bond linear polymer, the initiator, the free radical stabilizer and the antioxidant, adding the mixture into a single-screw extruder or a double-screw extruder, wherein the rotating speed of the single-screw extruder is 60-150r/min, the rotating speed of the double-screw extruder is 60-400r/min, the temperature of a feeding section of the single-screw extruder or the double-screw extruder is 160-fold-material 190 ℃, the temperature from a melting section to a neck mold is 180-fold-material 260 ℃, and extruding and granulating to obtain the ion-crosslinked high-melt-strength polypropylene.

The invention is further illustrated by the following specific examples.

The test methods or instruments used in the examples of the present invention are as follows:

and (3) determination of melt strength: adopting an RH-7D type capillary rheometer and a gottfert 'rheotens' melt strength tester;

melt flow rate: a SRZ-400E type melt flow rate tester was used.