CN113461880A - Polylactic acid injection molding method - Google Patents
Polylactic acid injection molding method Download PDFInfo
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- CN113461880A CN113461880A CN202110823680.7A CN202110823680A CN113461880A CN 113461880 A CN113461880 A CN 113461880A CN 202110823680 A CN202110823680 A CN 202110823680A CN 113461880 A CN113461880 A CN 113461880A
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- polylactic acid
- injection molding
- acid
- lactic acid
- molding method
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- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 132
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 131
- 238000001746 injection moulding Methods 0.000 title claims abstract description 52
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims abstract description 77
- 229920000642 polymer Polymers 0.000 claims abstract description 34
- 239000004310 lactic acid Substances 0.000 claims abstract description 32
- 235000014655 lactic acid Nutrition 0.000 claims abstract description 32
- 229920001400 block copolymer Polymers 0.000 claims abstract description 24
- 239000003054 catalyst Substances 0.000 claims abstract description 22
- GQOKIYDTHHZSCJ-UHFFFAOYSA-M dimethyl-bis(prop-2-enyl)azanium;chloride Chemical compound [Cl-].C=CC[N+](C)(C)CC=C GQOKIYDTHHZSCJ-UHFFFAOYSA-M 0.000 claims abstract description 18
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 18
- 238000007142 ring opening reaction Methods 0.000 claims abstract description 18
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 12
- 230000000379 polymerizing effect Effects 0.000 claims abstract description 8
- 229920001577 copolymer Polymers 0.000 claims abstract description 7
- 230000003197 catalytic effect Effects 0.000 claims abstract description 4
- 239000003999 initiator Substances 0.000 claims description 40
- CWERGRDVMFNCDR-UHFFFAOYSA-N thioglycolic acid Chemical compound OC(=O)CS CWERGRDVMFNCDR-UHFFFAOYSA-N 0.000 claims description 36
- 229960000448 lactic acid Drugs 0.000 claims description 32
- PYOKUURKVVELLB-UHFFFAOYSA-N trimethyl orthoformate Chemical compound COC(OC)OC PYOKUURKVVELLB-UHFFFAOYSA-N 0.000 claims description 22
- 238000001035 drying Methods 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 17
- 238000003756 stirring Methods 0.000 claims description 17
- FAPDDOBMIUGHIN-UHFFFAOYSA-K antimony trichloride Chemical group Cl[Sb](Cl)Cl FAPDDOBMIUGHIN-UHFFFAOYSA-K 0.000 claims description 14
- 238000002347 injection Methods 0.000 claims description 14
- 239000007924 injection Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 10
- 229910021641 deionized water Inorganic materials 0.000 claims description 10
- UEEJHVSXFDXPFK-UHFFFAOYSA-N N-dimethylaminoethanol Chemical group CN(C)CCO UEEJHVSXFDXPFK-UHFFFAOYSA-N 0.000 claims description 8
- 230000009471 action Effects 0.000 claims description 8
- 238000004821 distillation Methods 0.000 claims description 7
- YYROPELSRYBVMQ-UHFFFAOYSA-N p-toluenesulfonyl chloride Substances CC1=CC=C(S(Cl)(=O)=O)C=C1 YYROPELSRYBVMQ-UHFFFAOYSA-N 0.000 claims description 7
- KKBNUPMMAGEQAT-UHFFFAOYSA-N [4-(trifluoromethyl)phenyl]methanesulfonyl chloride Chemical compound FC(F)(F)C1=CC=C(CS(Cl)(=O)=O)C=C1 KKBNUPMMAGEQAT-UHFFFAOYSA-N 0.000 claims description 6
- 239000003513 alkali Substances 0.000 claims description 4
- 229930182843 D-Lactic acid Natural products 0.000 claims description 3
- JVTAAEKCZFNVCJ-UWTATZPHSA-N D-lactic acid Chemical compound C[C@@H](O)C(O)=O JVTAAEKCZFNVCJ-UWTATZPHSA-N 0.000 claims description 3
- 229940022769 d- lactic acid Drugs 0.000 claims description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 208000005156 Dehydration Diseases 0.000 description 8
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 description 8
- 230000018044 dehydration Effects 0.000 description 8
- 238000006297 dehydration reaction Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 238000001125 extrusion Methods 0.000 description 5
- 230000003179 granulation Effects 0.000 description 5
- 238000005469 granulation Methods 0.000 description 5
- 230000000977 initiatory effect Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 150000002978 peroxides Chemical class 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- DGMOBVGABMBZSB-UHFFFAOYSA-N 2-methylpropanoyl chloride Chemical compound CC(C)C(Cl)=O DGMOBVGABMBZSB-UHFFFAOYSA-N 0.000 description 3
- 238000004440 column chromatography Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 241000196324 Embryophyta Species 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 2
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium peroxydisulfate Substances [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- VAZSKTXWXKYQJF-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)OOS([O-])=O VAZSKTXWXKYQJF-UHFFFAOYSA-N 0.000 description 2
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 2
- 238000010560 atom transfer radical polymerization reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 150000001733 carboxylic acid esters Chemical class 0.000 description 2
- 229920002521 macromolecule Polymers 0.000 description 2
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 2
- 244000005700 microbiome Species 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 1
- 229920002261 Corn starch Polymers 0.000 description 1
- 240000003183 Manihot esculenta Species 0.000 description 1
- 235000016735 Manihot esculenta subsp esculenta Nutrition 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 150000001263 acyl chlorides Chemical class 0.000 description 1
- 238000000071 blow moulding Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 239000008120 corn starch Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 150000003014 phosphoric acid esters Chemical class 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 229920003225 polyurethane elastomer Polymers 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 description 1
- 238000009757 thermoplastic moulding Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/0001—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor characterised by the choice of material
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
- C08F226/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen by a single or double bond to nitrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
- C08G63/08—Lactones or lactides
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Polyesters Or Polycarbonates (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
The invention relates to a polylactic acid injection molding method, which comprises the following steps: step 1, lactic acid primary polycondensation: firstly, dehydrating lactic acid, and then polycondensing the lactic acid into a polylactic acid primary polymer under the catalytic action of a first catalyst; step 2, depolymerization of the primary polymer: depolymerizing the polylactic acid primary polymer to obtain a polylactic acid prepolymer; step 3, ring opening and block polymerization: ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyl diallyl ammonium chloride to obtain a polylactic acid segmented copolymer; step 4, injection molding: adding the polylactic acid block copolymer into an injection molding machine for injection molding. The invention solves the problems of the existing injection molding method of polylactic acid, namely, the prepared polylactic acid not only has improved mechanical property and toughness, but also can ensure the processability and transparency of the polylactic acid, so that the polylactic acid can be applied to most industries.
Description
Technical Field
The invention relates to the field of polyurethane elastomers, in particular to a polylactic acid injection molding method.
Background
The polylactic acid is a polymer polymerized by using lactic acid as a main raw material, can be synthesized by renewable plant resources, such as corn starch, cassava starch, plant fiber, biosaccharides and the like, has low synthesis energy consumption and no pollution, and is beneficial to ecological cycle; the polylactic acid has good biodegradability, does not release toxic gases such as nitrides, sulfides and the like after incineration, can be completely degraded by microorganisms in the nature after being buried, finally generates carbon dioxide and water, and does not pollute the environment; and the polylactic acid has good processing performance and mechanical property, is equivalent to the performance of general plastics of polystyrene and polyethylene glycol terephthalate, and is expected to become a substitute product of petroleum-based general plastics. However, although the polylactic acid prepared by the existing injection molding method of polylactic acid is improved in mechanical property and toughness, the processability of the polylactic acid is reduced, and the color is deepened seriously, so that the application of the polylactic acid in some industries is hindered.
Disclosure of Invention
The invention aims to provide a polylactic acid injection molding method, which aims to solve the problems that the processability of polylactic acid is reduced, the color is deepened seriously, and the application of the polylactic acid in part of industries is hindered although the mechanical property and the toughness of the polylactic acid prepared by the existing polylactic acid injection molding method are improved.
The purpose of the invention is realized by adopting the following technical scheme:
a polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
firstly, dehydrating lactic acid, and then polycondensing the lactic acid into a polylactic acid primary polymer under the catalytic action of a first catalyst;
step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer under the conditions of high temperature and reduced pressure to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
under the action of an initiator and a second catalyst, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyl diallyl ammonium chloride to obtain a polylactic acid segmented copolymer;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a co-rotating twin-screw machine, extruding and granulating the polylactic acid block copolymer, and adding the polylactic acid block copolymer into an injection molding machine for injection molding.
Preferably, the method of dehydration of lactic acid is: stirring lactic acid and trimethyl orthoformate at room temperature for 2-5 h, wherein the mass ratio of the lactic acid to the trimethyl orthoformate is 10: 0.1-0.4.
Preferably, the lactic acid is one or more of L-lactic acid, D-lactic acid and DL-lactic acid.
Preferably, the first catalyst is antimony chloride.
Preferably, the second catalyst is N, N-dimethylethanolamine.
Preferably, the initiator is obtained by reacting 4-trifluoromethyl-alpha-tosyl chloride with 2-mercaptoacetic acid in alkali liquor.
Preferably, the injection pressure of the injection molding machine is 93.45-96.82 MPa, and the injection speed is 58-66 cm3And/s, the temperature of the machine barrel is 180-200 ℃, and the temperature of the die is 50-100 ℃.
Preferably, the reaction process of the polycondensation in the step 1 is as follows:
adding a first catalyst into the dehydrated lactic acid, uniformly mixing, carrying out reduced pressure distillation treatment for 2h at 40-50 ℃ under the pressure of 0.1Mpa, and then drying and recrystallizing to obtain a polylactic acid primary polymer;
wherein the mass ratio of the lactic acid to the first catalyst is 10: 0.04-0.06.
Preferably, the solvent used for recrystallization is dichloromethane.
Preferably, the high temperature in the step 2 is 120-160 ℃, and the pressure is lower than 100Pa when the pressure is reduced.
Preferably, the preparation process of the initiator is as follows:
fully mixing 2-mercaptoacetic acid with deionized water, dropwise adding alkali liquor until the pH value of the mixed liquor is 12.5-13.0, then adding 4-trifluoromethyl-alpha-tosyl chloride at room temperature while stirring, then continuously stirring for reaction for 2-5 h, and sequentially extracting, concentrating, drying and passing through a column to obtain an initiator;
wherein the mass ratio of the 2-mercaptoacetic acid to the deionized water is 1.2-1.6: 10, and the molar ratio of the 2-mercaptoacetic acid to the 4-trifluoromethyl-alpha-toluenesulfonyl chloride is 5.8-6.5: 5.
Preferably, the alkali liquor is a sodium hydroxide solution or a potassium hydroxide solution with the concentration of 0.01-0.1 mol/L.
Preferably, the extraction is carried out using a carboxylic acid ester or a phosphoric acid ester as an extractant.
Preferably, in the step 3, the mass ratio of the initiator, the second catalyst, the polylactic acid prepolymer and the dimethyldiallylammonium chloride is 0.01-0.04: 0.02-0.05: 1.7-2.5: 1.
Preferably, the polymerization temperature in the step 3 is 25-45 ℃, and the polymerization time is 2-6 h.
The invention has the beneficial effects that:
1. the invention provides a polylactic acid injection molding method, which solves the problems of the existing polylactic acid injection molding method, namely the polylactic acid prepared by the invention is improved in the aspects of mechanical property and toughness, and the processability and transparency of the polylactic acid can be ensured, so that the polylactic acid can be applied to most industries.
2. In the prior art, many modifications of toughness of polylactic acid are carried out, so that the application range of the polylactic acid is expected to be expanded. Such as: although the polymer block synthesized by polylactic acid and poly 2-methyl-1, 3-butadiene has better flexibility, poly 2-methyl-1, 3-butadiene has the defect of poor processability, but the processability of polylactic acid is influenced, and poly 2-methyl-1, 3-butadiene has darker color and has larger influence on the transparency of polylactic acid. According to the invention, the block of the polylactic acid is optimized according to the needs, and the poly dimethyl diallyl ammonium chloride is used as a block material to be embedded in the middle of the polylactic acid, so that the multi-block polymerized polylactic acid block copolymer is finally obtained. Compared with the block polymer formed by poly 2-methyl-1, 3-butadiene and polylactic acid, the block polymer of poly dimethyl diallyl ammonium chloride and polylactic acid has lighter color and higher transparency, and the poly dimethyl diallyl ammonium chloride is rich in polar molecules, so that the hydrophilicity of the polylactic acid can be improved, and the hydrophilic modification of the polylactic acid is not needed.
3. According to the invention, polylactic acid is synthesized by a direct polycondensation method, and then trimethyl orthoformate is added in the dehydration treatment process of the lactic acid through ring opening, wherein the trimethyl orthoformate can promote the dehydration of the lactic acid and can be decomposed with water to obtain methyl formate and methanol, the methyl formate is volatilized at room temperature and can be easily removed, and the methanol is used as a donor and an acceptor of a hydrogen bond and can simultaneously activate antimony chloride and a low molecular weight polymer, so that the reaction activity of a low molecular weight polymer chain can be improved, the catalytic polycondensation and depolymerization effects of the antimony chloride are promoted, and the generation of a polylactic acid intermediate product is effectively increased.
4. Compared with the multi-stage initiation polymerization reaction, the invention selects the reactant of 2-mercaptoacetic acid and 4-trifluoromethyl-alpha-toluene sulfonyl chloride as the initiator, the initiator can play the role of initiation under the action of normal temperature illumination, the initiator can cooperate with the catalyst N, N-dimethyl ethanolamine to sequentially complete ring opening and further polymerization of the cyclized polylactic acid prepolymer, compared with the conventional peroxide initiator, the side reaction is less, compared with the common acyl chloride initiator, the initiation temperature is lower, the activity is stronger, and under the condition of the same addition amount and the catalyst, the relative molecular weight of the polymer prepared by the initiator used in the invention is more concentrated.
Detailed Description
For the purpose of more clearly illustrating the present invention and more clearly understanding the technical features, objects and advantages of the present invention, the technical solutions of the present invention will now be described in detail below, but are not to be construed as limiting the implementable scope of the present invention.
Polylactic acid is a biodegradable material, has good biodegradability, can be completely degraded by microorganisms in the nature after being used, finally generates carbon dioxide and water, does not pollute the environment, is very favorable for protecting the environment, and is a well-known environment-friendly material; the mechanical property and physical property are good, and the method is suitable for various processing methods such as blow molding, thermoplastic molding and the like, and has convenient processing and wide application. However, polylactic acid has a large number of ester bonds and poor hydrophilicity, so that the biocompatibility of the polylactic acid with other substances is reduced; the product obtained by polymerization has too wide relative molecular weight distribution, and the polylactic acid is a linear polymer, so that the strength of the polylactic acid material is often not satisfactory, the brittleness is high, the heat distortion temperature is low (54 ℃ under the load of 0146 MPa), and the impact resistance is poor.
Besides the slow progress of the polymerization reaction and the weak reactivity of the polymerization grafting reaction, the improper selection of the initiator can also cause the initiation reaction to progress unevenly, thereby affecting the hardness and toughness of the product. When the initiator at normal temperature is selected conventionally, a peroxide initiator is mostly selected, and although the peroxide initiator has a good initiating effect at low temperature, the peroxide initiator is easy to decompose by itself due to the existence of a peroxide bond, and further explosive gas is generated, so the reaction process is relatively dangerous.
According to the invention, a macromolecule initiator with a carboxyl end is obtained by selecting 4-trifluoromethyl-alpha-tosyl chloride to react with a sulfydryl on 2-mercaptoacetic acid, and an Atom Transfer Radical Polymerization (ATRP) initiated by the macromolecule initiator can initiate a monomer to polymerize into a block copolymer with controllable molecular weight, narrow molecular weight distribution and less byproducts at normal temperature.
The invention is further described below with reference to the following examples.
Example 1
A polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
mixing L-lactic acid and trimethyl orthoformate according to a mass ratio of 10:0.25, stirring at room temperature for 3 hours, then completing dehydration treatment, adding antimony chloride into the dehydrated lactic acid, uniformly mixing, performing reduced pressure distillation treatment at 45 ℃ and 0.1Mpa for 2 hours, then drying and recrystallizing with dichloromethane to obtain a polylactic acid primary polymer; wherein the mass ratio of the lactic acid to the antimony chloride is 10: 0.05.
Step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer at 140 ℃ and under the pressure of less than 100Pa to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
at the temperature of 30 ℃, under the action of an initiator and N, N-dimethylethanolamine, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyldiallylammonium chloride to obtain a polylactic acid block copolymer; wherein the mass ratio of the initiator, the second catalyst, the polylactic acid prepolymer and the dimethyl diallyl ammonium chloride is 0.02:0.03:2.2: 1;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a homodromous twin-screw machine, and setting the injection pressure to be 95.32MPa and the injection speed to be 62cm3And/s, the temperature of a machine barrel is 180-200 ℃, the temperature of a die is 50-100 ℃, and the mixture is added into an injection molding machine for injection molding after extrusion and granulation.
Wherein the preparation process of the initiator comprises the following steps:
fully mixing 2-mercaptoacetic acid and deionized water, dropwise adding 0.05mol/L sodium hydroxide solution until the pH of the mixed solution is 12.5-13.0, then adding 4-trifluoromethyl-alpha-tosyl chloride at room temperature while stirring, then continuously stirring for reaction for 2-5 h, and sequentially carrying out carboxylic ester extraction, concentration, drying and column chromatography to obtain an initiator;
wherein the mass ratio of the 2-mercaptoacetic acid to the deionized water is 1.4:10, and the molar ratio of the 2-mercaptoacetic acid to the 4-trifluoromethyl-alpha-toluenesulfonyl chloride is 6.2: 5.
Example 2
A polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
mixing D-lactic acid and trimethyl orthoformate according to a mass ratio of 10:0.1, stirring at room temperature for 5 hours, then completing dehydration treatment, adding antimony chloride into the dehydrated lactic acid, uniformly mixing, performing reduced pressure distillation treatment at 40 ℃ and 0.1Mpa for 2 hours, then drying and recrystallizing with dichloromethane to obtain a polylactic acid primary polymer; wherein the mass ratio of the lactic acid to the antimony chloride is 10: 0.04.
Step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer at the temperature of 120 ℃ and under the pressure of less than 100Pa to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
at the temperature of 25 ℃, under the action of an initiator and N, N-dimethylethanolamine, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyldiallylammonium chloride to obtain a polylactic acid block copolymer; wherein the mass ratio of the initiator, the second catalyst, the polylactic acid prepolymer and the dimethyl diallyl ammonium chloride is 0.01:0.02:1.7: 1;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a homodromous twin-screw machine, setting the injection pressure to 93.45MPa and the injection speed to 58cm3And/s, the temperature of a machine barrel is 180-200 ℃, the temperature of a die is 50-100 ℃, and the mixture is added into an injection molding machine for injection molding after extrusion and granulation.
Wherein the preparation process of the initiator comprises the following steps:
fully mixing 2-mercaptoacetic acid with deionized water, dropwise adding 0.01mol/L potassium hydroxide solution until the pH of the mixed solution is 12.5-13.0, then adding 4-trifluoromethyl-alpha-tosyl chloride at room temperature while stirring, then continuously stirring for reaction for 2-5 h, and sequentially performing phosphate extraction, concentration, drying and column chromatography to obtain an initiator;
wherein the mass ratio of the 2-mercaptoacetic acid to the deionized water is 1.2:10, and the molar ratio of the 2-mercaptoacetic acid to the 4-trifluoromethyl-alpha-toluenesulfonyl chloride is 5.8: 5.
Example 3
A polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
mixing DL-lactic acid and trimethyl orthoformate according to a mass ratio of 10:0.4, stirring at room temperature for 5 hours, then completing dehydration treatment, adding antimony chloride into the dehydrated lactic acid, uniformly mixing, performing reduced pressure distillation treatment at 50 ℃ and 0.1Mpa for 2 hours, then drying and recrystallizing with dichloromethane to obtain a polylactic acid primary polymer; wherein the mass ratio of the lactic acid to the antimony chloride is 10: 0.06.
Step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer at the temperature of 160 ℃ and under the pressure of less than 100Pa to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
at the temperature of 45 ℃, under the action of an initiator and N, N-dimethylethanolamine, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyldiallylammonium chloride to obtain a polylactic acid block copolymer; wherein the mass ratio of the initiator, the second catalyst, the polylactic acid prepolymer and the dimethyl diallyl ammonium chloride is 0.04:0.05:2.5: 1;
step 4, injection molding:
drying the polylactic acid segmented copolymer, and then placing the dried polylactic acid segmented copolymer in a co-rotating twin-screw extruder, wherein the injection pressure is set to be 93.45-96.82 MPa, and the injection speed is set to be 58-66 cm3And/s, the temperature of a machine barrel is 180-200 ℃, the temperature of a die is 50-100 ℃, and the mixture is added into an injection molding machine for injection molding after extrusion and granulation.
Wherein the preparation process of the initiator comprises the following steps:
fully mixing 2-mercaptoacetic acid with deionized water, dropwise adding 0.1mol/L sodium hydroxide solution until the pH of the mixed solution is 12.5-13.0, then adding 4-trifluoromethyl-alpha-tosyl chloride at room temperature while stirring, then continuously stirring for reaction for 2-5 h, and sequentially performing phosphate extraction, concentration, drying and column chromatography to obtain an initiator;
wherein the mass ratio of the 2-mercaptoacetic acid to the deionized water is 1.2-1.6: 10, and the molar ratio of the 2-mercaptoacetic acid to the 4-trifluoromethyl-alpha-toluenesulfonyl chloride is 5.8-6.5: 5.
Comparative example 1
A polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
mixing L-lactic acid and trimethyl orthoformate according to a mass ratio of 10:0.25, stirring at room temperature for 3 hours, then completing dehydration treatment, adding antimony chloride into the dehydrated lactic acid, uniformly mixing, performing reduced pressure distillation treatment at 45 ℃ and 0.1Mpa for 2 hours, then drying and recrystallizing with dichloromethane to obtain a polylactic acid primary polymer; wherein the mass ratio of the lactic acid to the antimony chloride is 10: 0.05.
Step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer at 140 ℃ and under the pressure of less than 100Pa to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
at the temperature of 30 ℃, under the action of initiator ammonium persulfate and N, N-dimethylethanolamine, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer and dimethyldiallylammonium chloride to obtain a polylactic acid segmented copolymer; wherein the mass ratio of the initiator ammonium persulfate, the second catalyst, the polylactic acid prepolymer and the dimethyl diallyl ammonium chloride is 0.02:0.03:2.2: 1;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a homodromous twin-screw machine, and setting the injection pressure to be 95.32MPa and the injection speed to be 62cm3And/s, the temperature of a machine barrel is 180-200 ℃, the temperature of a die is 50-100 ℃, and the mixture is added into an injection molding machine for injection molding after extrusion and granulation.
Comparative example 2
A polylactic acid injection molding method comprises the following steps:
step 1, lactic acid primary polycondensation:
mixing L-lactic acid and trimethyl orthoformate according to a mass ratio of 10:0.25, stirring at room temperature for 3 hours, then completing dehydration treatment, adding antimony chloride into the dehydrated lactic acid, uniformly mixing, performing reduced pressure distillation treatment at 45 ℃ and 0.1Mpa for 2 hours, then drying and recrystallizing with dichloromethane to obtain a polylactic acid primary polymer; wherein the mass ratio of the lactic acid to the antimony chloride is 10: 0.05.
Step 2, depolymerization of the primary polymer:
treating the polylactic acid primary polymer at 140 ℃ and under the pressure of less than 100Pa to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
at the temperature of 30 ℃, under the action of initiators of isobutyryl chloride and N, N-dimethylethanolamine, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyldiallylammonium chloride to obtain a polylactic acid segmented copolymer; wherein the mass ratio of the initiator isobutyryl chloride, the second catalyst, the polylactic acid prepolymer and the dimethyl diallyl ammonium chloride is 0.02:0.03:2.2: 1;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a homodromous twin-screw machine, and setting the injection pressure to be 95.32MPa and the injection speed to be 62cm3And/s, the temperature of a machine barrel is 180-200 ℃, the temperature of a die is 50-100 ℃, and the mixture is added into an injection molding machine for injection molding after extrusion and granulation.
For a more clear description of the present invention, the present invention was also examined in terms of performance of the polylactic acids prepared in examples 1 to 3 and comparative examples 1 to 2. The tensile strength, elongation at break and impact strength were measured according to the method described in GB/T1039-.
The results are shown in the following table.
| Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 | |
| Tensile Strength (MPa) | 67.2 | 64.3 | 68.9 | 62.7 | 48.2 |
| Elongation at Break (%) | 249.4 | 263.8 | 237.5 | 211.4 | 187.5 |
| Impact Strength (KJ/m)2) | 84.5 | 76.1 | 80.7 | 71.2 | 65.8 |
| Light transmittance (%) | 84.2 | 85.7 | 82.0 | 67.4 | 74.3 |
As can be seen from the above table, the comparative example has lower light transmittance and lower impact strength compared with examples 1 to 3 of the present invention, and the suspected reason may be that the polylactic acid block copolymer generated by polymerization initiated by the initiator peroxide (sodium persulfate) in comparative example 1 has more side reactions; comparative example 2 had lower tensile strength, elongation at break, impact strength and light transmittance than examples 1 to 3, and it is suspected that the initiator isobutyryl chloride in comparative example 2 was not suitable for the synthesis of the polylactic acid block copolymer of the present invention.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. The polylactic acid injection molding method is characterized by comprising the following steps:
step 1, lactic acid primary polycondensation:
firstly, dehydrating lactic acid, and then polycondensing the lactic acid into a polylactic acid primary polymer under the catalytic action of a first catalyst;
step 2, depolymerization of the primary polymer:
depolymerizing the polylactic acid primary polymer to obtain a polylactic acid prepolymer;
step 3, ring opening and block polymerization:
under the action of an initiator and a second catalyst, ring-opening the polylactic acid prepolymer, and polymerizing the polylactic acid prepolymer with dimethyl diallyl ammonium chloride to obtain a polylactic acid segmented copolymer;
step 4, injection molding:
drying the polylactic acid block copolymer, placing the dried polylactic acid block copolymer in a co-rotating twin-screw machine, extruding and granulating the polylactic acid block copolymer, and adding the polylactic acid block copolymer into an injection molding machine for injection molding.
2. The injection molding method of claim 1, wherein the lactic acid is dehydrated by: stirring lactic acid and trimethyl orthoformate at room temperature for 2-5 h, wherein the mass ratio of the lactic acid to the trimethyl orthoformate is 10: 0.1-0.4.
3. The injection molding method of claim 1, wherein the lactic acid is one or more of L-lactic acid, D-lactic acid, and DL-lactic acid.
4. The injection molding method of claim 1, wherein the first catalyst is antimony chloride and the second catalyst is N, N-dimethylethanolamine.
5. The injection molding method of claim 1, wherein in step 3, the mass ratio of the initiator, the second catalyst, the polylactic acid prepolymer and the dimethyldiallylammonium chloride is 0.01-0.04: 0.02-0.05: 1.7-2.5: 1.
6. The injection molding method of claim 1, wherein in step 3, the polymerization temperature in step 3 is 25-45 ℃ and the polymerization time is 2-6 h.
7. The injection molding method of polylactic acid according to claim 1, wherein the injection pressure of the injection molding machine is 93.45-96.82 MPa, and the injection speed is 58-66 cm3And/s, the temperature of the machine barrel is 180-200 ℃, and the temperature of the die is 50-100 ℃.
8. The injection molding method of claim 1, wherein the polycondensation in step 1 comprises the following steps:
adding a first catalyst into the dehydrated lactic acid, uniformly mixing, carrying out reduced pressure distillation treatment for 2h at 40-50 ℃ under the pressure of 0.1Mpa, and then drying and recrystallizing to obtain a polylactic acid primary polymer;
wherein the mass ratio of the lactic acid to the first catalyst is 10: 0.04-0.06.
9. The injection molding method of claim 1, wherein the depolymerization in step 2 is carried out at a temperature of 120-160 ℃ and a pressure of less than 100 Pa.
10. The injection molding method of claim 1, wherein the initiator is prepared by the following steps:
fully mixing 2-mercaptoacetic acid with deionized water, dropwise adding alkali liquor until the pH value of the mixed liquor is 12.5-13.0, then adding 4-trifluoromethyl-alpha-tosyl chloride at room temperature while stirring, then continuously stirring for reaction for 2-5 h, and sequentially extracting, concentrating, drying and passing through a column to obtain an initiator;
wherein the mass ratio of the 2-mercaptoacetic acid to the deionized water is 1.2-1.6: 10, and the molar ratio of the 2-mercaptoacetic acid to the 4-trifluoromethyl-alpha-toluenesulfonyl chloride is 5.8-6.5: 5.
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