CN112409629A - Foaming forming method of modified amorphous polylactic acid - Google Patents
Foaming forming method of modified amorphous polylactic acid Download PDFInfo
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- CN112409629A CN112409629A CN202011299145.8A CN202011299145A CN112409629A CN 112409629 A CN112409629 A CN 112409629A CN 202011299145 A CN202011299145 A CN 202011299145A CN 112409629 A CN112409629 A CN 112409629A
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- polylactic acid
- amorphous polylactic
- foaming
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- chain extender
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- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 84
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 83
- 238000005187 foaming Methods 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000012530 fluid Substances 0.000 claims abstract description 30
- 239000004970 Chain extender Substances 0.000 claims abstract description 27
- 239000002667 nucleating agent Substances 0.000 claims abstract description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 230000004048 modification Effects 0.000 claims abstract description 15
- 238000012986 modification Methods 0.000 claims abstract description 15
- 239000011324 bead Substances 0.000 claims abstract description 13
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 10
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 239000002994 raw material Substances 0.000 claims description 23
- 238000000465 moulding Methods 0.000 claims description 14
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 10
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000001125 extrusion Methods 0.000 claims description 6
- 238000010097 foam moulding Methods 0.000 claims description 6
- 229920000728 polyester Polymers 0.000 claims description 6
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 5
- 239000001569 carbon dioxide Substances 0.000 claims description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 4
- 239000004593 Epoxy Substances 0.000 claims description 3
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 3
- FPAFDBFIGPHWGO-UHFFFAOYSA-N dioxosilane;oxomagnesium;hydrate Chemical compound O.[Mg]=O.[Mg]=O.[Mg]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O FPAFDBFIGPHWGO-UHFFFAOYSA-N 0.000 claims description 3
- 230000008595 infiltration Effects 0.000 claims description 3
- 238000001764 infiltration Methods 0.000 claims description 3
- 239000010445 mica Substances 0.000 claims description 3
- 229910052618 mica group Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 239000004408 titanium dioxide Substances 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 239000000047 product Substances 0.000 description 22
- 239000002245 particle Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 6
- 239000013078 crystal Substances 0.000 description 4
- 230000009477 glass transition Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 239000006260 foam Substances 0.000 description 3
- 239000002121 nanofiber Substances 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 239000006261 foam material Substances 0.000 description 2
- 239000004088 foaming agent Substances 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 210000000497 foam cell Anatomy 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920000118 poly(D-lactic acid) Polymers 0.000 description 1
- 229920001432 poly(L-lactide) Polymers 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000011265 semifinished product Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
-
- 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
- C08G63/91—Polymers modified by chemical after-treatment
- C08G63/912—Polymers modified by chemical after-treatment derived from hydroxycarboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0066—Use of inorganic compounding ingredients
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/16—Making expandable particles
- C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/22—After-treatment of expandable particles; Forming foamed products
- C08J9/228—Forming foamed products
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/06—CO2, N2 or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/08—Supercritical fluid
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/24—Acids; Salts thereof
- C08K3/26—Carbonates; Bicarbonates
- C08K2003/265—Calcium, strontium or barium carbonate
Abstract
A foaming forming method of modified amorphous polylactic acid comprises the following steps: step 1, modifying amorphous polylactic acid by using a modification auxiliary agent, wherein the modification auxiliary agent is one or more of a chain extender and a nucleating agent; step 2, placing the modified amorphous polylactic acid into an autoclave, and performing high-pressure permeation by using a supercritical fluid to infiltrate the modified amorphous polylactic acid by using the supercritical fluid so as to obtain pre-expanded beads; and 3, placing the pre-foamed beads into a water bath or an oil bath, foaming the pre-foamed beads in a mold inside the water bath or the oil bath for 1-14 min at the temperature of 60-90 ℃, and cooling to obtain a molded foamed product.
Description
Technical Field
The invention relates to a foaming forming method, in particular to a foaming forming method of modified amorphous polylactic acid.
Background
At present, most of the foaming materials in the market applied to the field of packaging and boxes are traditional polymer materials such as PP, PS and the like, but the traditional polymer materials are cheap in raw materials, but have the disadvantages of being unrecoverable and causing a great deal of pollution to the environment. Under the urgent environment of environmental protection problem and the promulgation of government 'plastic limit order', the urgent situation is that: the novel recyclable foaming raw material is searched, the related foaming forming technology is developed, and the novel recyclable foaming raw material can replace the traditional high polymer foaming material in the application level.
Polylactic acid (PLA), also known as polylactide, is a polyester polymer obtained by polymerizing lactic acid as a main raw material, and is a novel biodegradable material. However, polylactic acid has very low melt strength and is difficult to foam and mold, and therefore, it is necessary to modify the raw material. Such as:
(1) the invention of China application CN109825046A is a biodegradable polylactic acid foaming particle, which mixes dextrorotatory polylactic acid, levorotatory polylactic acid, plasticizer and foam cell nucleating agent, and modifies polylactic acid, thereby realizing the biodegradability of the foaming product and improving the melt strength of the polylactic acid.
However, the above-mentioned polylactic acids (poly (d-lactic acid) and poly (l-lactic acid)) actually contain a certain amount of crystals, which cannot achieve complete degradation, and thus cannot achieve 100% non-pollution effect. In addition, the above modification techniques also cannot achieve direct molding of foamed products, but require first foaming into particles and then welding the particles together, which limits the improvement of the manufacturing efficiency of foamed products.
(2) The Chinese patent application CN111286070A discloses a supercritical fluid injection-molded foamed polylactic acid foam material and a preparation method thereof, wherein the crystallization property and the melt property of the polylactic acid material are improved by using cellulose nanofibers as nucleating agents, and a microporous foamed cellulose nanofiber/polylactic acid composite material with uniform cell size, high cell density and good performance is prepared.
However, the cellulose nanofiber/polylactic acid composite material needs to be extruded and molded by an injection molding machine, and needs to be heated and melted at the same time, so that the manufacturing cost of the foam material is greatly increased. In addition, the polylactic acid cannot be completely degraded, and thus cannot achieve 100% pollution-free effect.
At present, PLA4060D (amorphous polylactic acid) developed by Naturework in the United states does not contain any crystal, and is characterized in that the crystallinity is kept at 0% all the time before and after foaming, and the used product is more favorable for being decomposed into substances which do not pollute the environment under natural or specific conditions, and the relative decomposition rate is faster and more thorough.
However, the amorphous polylactic acid has lower melt strength than that of the general polylactic acid, which is very unfavorable for foaming and molding, and the amorphous polylactic acid cannot be directly formed into a foamed product by the conventional foaming method.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for foam molding of a modified amorphous polylactic acid, comprising: the foam molding method comprises the following steps:
step 1, modifying amorphous polylactic acid by using a modification auxiliary agent, wherein the modification auxiliary agent is one or more of a chain extender and a nucleating agent;
step 2, placing the modified amorphous polylactic acid into an autoclave, and performing high-pressure permeation by using a supercritical fluid to infiltrate the modified amorphous polylactic acid by using the supercritical fluid so as to obtain pre-expanded beads;
and 3, placing the pre-foamed beads into a water bath or an oil bath, foaming the pre-foamed beads in a mold inside the water bath or the oil bath for 1-14 min at the temperature of 60-90 ℃, and cooling to obtain a molded foamed product.
Further, in the step 1, a chain extender is used for modifying the amorphous polylactic acid, or the chain extender and a nucleating agent are used for modifying the amorphous polylactic acid, wherein the adding amount of the chain extender is 1 wt% -1.5 wt%.
Further, the chain extender is one or more of a polyester chain extender and an epoxy chain extender.
Further, a nucleating agent is used for modifying the amorphous polylactic acid, or a chain extender and the nucleating agent are used for modifying the amorphous polylactic acid, and the addition amount of the nucleating agent is 1 wt% -2 wt%.
Further, the nucleating agent is one or more of calcium carbonate, talcum powder, mica powder, argil, zinc oxide powder and titanium dioxide.
Further, in the step 2, pressure maintaining permeation is performed for 10-100 min under the pressure of 1-6 MPa.
Further, in step 2, the permeation amount of the supercritical fluid is 8% to 20% by weight.
Further, in step 2, the supercritical fluid is one of a carbon dioxide supercritical fluid and a nitrogen supercritical fluid.
After the technical scheme is adopted, the invention has the effects that:
(1) the invention adopts the amorphous polylactic acid as the raw material, and the amorphous polylactic acid does not contain any crystal, so the crystallinity of the amorphous polylactic acid before and after foaming is always kept at 0 percent, complete degradation can be realized, and the technical effect of zero pollution is achieved.
(2) The invention firstly modifies the amorphous polylactic acid to expand molecular chains and increase molecular weight, so that the amorphous polylactic acid can not absorb excessive supercritical fluid; then, performing high-pressure permeation in a high-pressure kettle by using a supercritical fluid to reduce the glass transition temperature (55-60 ℃) of the amorphous polylactic acid; and finally, the most important point is that the foaming is carried out for 1-14 min at the temperature of 60-90 ℃ in a water bath or oil bath, the foaming is carried out by selecting the temperature slightly higher than the glass transition temperature of the amorphous polylactic acid, and meanwhile, the foaming time is accurately controlled, so that the foamed product is smoothly formed and has good appearance and physical properties.
Drawings
FIG. 1 is a flow chart of a foam molding method according to the present invention;
FIG. 2 is a scanning electron micrograph of the foam of the present invention.
Detailed Description
The technical solution of the present invention is further described by the following examples:
the invention provides a foaming forming method of modified amorphous polylactic acid, as shown in figure 1, the foaming forming method comprises the following steps:
step 1, modifying amorphous polylactic acid (namely polylactic acid with the crystallinity of 0 percent, such as PLA4060D of Naturework) by using a modification auxiliary agent, wherein the modification auxiliary agent is one or more of a chain extender and a nucleating agent;
step 2, placing the modified amorphous polylactic acid into a high-pressure kettle, and performing high-pressure permeation by using a supercritical fluid to infiltrate the modified amorphous polylactic acid by using the supercritical fluid so as to obtain pre-foamed beads (namely semi-finished product particles);
and 3, placing the pre-foamed beads into a water bath or an oil bath, foaming the pre-foamed beads in a mold inside the water bath or the oil bath for 1-14 min at the temperature of 60-90 ℃, and cooling to obtain a molded foamed product.
The invention adopts the amorphous polylactic acid as the raw material, and the amorphous polylactic acid does not contain any crystal, so the crystallinity of the amorphous polylactic acid before and after foaming is always kept at 0 percent, complete degradation can be realized, and the technical effect of zero pollution is achieved.
In addition, the amorphous polylactic acid is modified to expand molecular chains and increase molecular weight, so that the amorphous polylactic acid cannot absorb excessive supercritical fluid; then, performing high-pressure permeation in a high-pressure kettle by using a supercritical fluid to reduce the glass transition temperature (55-60 ℃) of the amorphous polylactic acid; and finally, the most important point is that the foaming is carried out for 1-14 min at the temperature of 60-90 ℃ in a water bath or oil bath, the foaming is carried out by selecting the temperature slightly higher than the glass transition temperature of the amorphous polylactic acid, and meanwhile, the foaming time is accurately controlled, so that the foamed product is smoothly formed and has good appearance and physical properties.
Modification of amorphous polylactic acid
Specifically, in step 1, the modification of the amorphous polylactic acid specifically comprises the following steps:
step 1.1, mixing a modification auxiliary agent with polylactic acid to obtain a mixed raw material;
step 1.2, putting the raw materials into extrusion equipment, and extruding the raw materials through the extrusion equipment;
and step 1.3, cutting the raw materials to obtain the mixed long-strip blocky raw materials.
Wherein, in the step 1.2, the extrusion equipment is double-screw or single-screw extrusion equipment; in step 1.3, the raw material is cut directly or under water, and the length of the cut strip-shaped block-shaped raw material is 1.5 cm.
As an embodiment of the present invention, step 1 further includes: putting the modified amorphous polylactic acid into a mould; in step 2, the method further comprises: placing the mold into an autoclave; in step 3, the method further comprises: the mold is placed in a water bath or oil bath. The raw materials are put into the die in advance in the mode, the die can be directly transferred in the transferring process of each step, the raw materials do not need to be transferred independently, and the efficiency is improved. Among them, since the raw material needs to be foamed twice (pre-foaming and final foam molding) in the mold, the size of the mold needs to be precisely selected.
As another embodiment of the present invention, in step 2, the modified amorphous polylactic acid is directly placed in an autoclave without being placed in a mold; in step 3, the pre-expanded beads are then placed in a mold inside a water or oil bath. With the above-described method, since the raw material is foamed (final foam molding) only once in the mold, it is easier to control the size of the selected mold.
Specifically, in step 1, a chain extender is used to modify the amorphous polylactic acid, or a chain extender and a nucleating agent are used to modify the amorphous polylactic acid, wherein the addition amount of the chain extender is 1 wt% to 1.5 wt%.
Specifically, in step 1, a nucleating agent is used to modify the amorphous polylactic acid, or a chain extender and a nucleating agent are used to modify the amorphous polylactic acid, and the addition amount of the nucleating agent is 1 wt% to 2 wt%.
More specifically, in step 1, the chain extender is one or more of a polyester chain extender and an epoxy chain extender; the nucleating agent is one or more of calcium carbonate, talcum powder, mica powder, argil, zinc oxide powder and titanium dioxide.
High pressure permeation of supercritical fluids
Specifically, in the step 2, pressure-maintaining permeation is performed for 10-100 min under the pressure of 1-6 MPa.
Specifically, in step 2, the permeation amount of the supercritical fluid is 8% to 20% by weight, preferably 15% to 17.5% by weight.
Specifically, in step 2, the supercritical fluid is one of a carbon dioxide supercritical fluid and a nitrogen supercritical fluid.
Foaming molding
Specifically, in the step 3, the cooling time is 1-10 min. The final density of the product can be controlled by controlling the weight of the placed particles, the foaming and molding temperature and the cooling time, as shown in fig. 2, the density range of the obtained finished product is 50-150 g/L, and the pore size is 0.1-2 mm.
The foamed product prepared by the foaming forming method can be used for a chilled product packaging box, a foam transport box and the like, and products with different densities can be obtained by changing process parameters according to the application requirements of the products.
Example 1
Modifying the amorphous polylactic acid by using 1 wt% of polyester chain extender and 1 wt% of calcium carbonate, and putting the modified amorphous polylactic acid into a mould; putting the mould into a high-pressure kettle, introducing carbon dioxide supercritical fluid, and performing pressure-maintaining permeation for 20min under the condition that the pressure is 3Mpa, wherein the permeation quantity of the supercritical fluid is 16% by weight; and (3) placing the mould into a water bath or an oil bath, foaming for 2min at the temperature of 80 ℃, and cooling for 2min to obtain a molded foaming product. The products have a similar compressive stress, a higher compressive modulus and a similar flexural strength to EPP under the standard tests of DIN53421 and ISO 1209.
Example 2
Unlike example 1, in this example, in step 3, the mold was placed in a water bath or oil bath and foamed at a temperature of 55 ℃. The foamed product has poor forming effect, can not be tightly combined among particles, and has larger combination defect and poorer physical and mechanical properties.
Example 3
Unlike example 1, in this example, in step 3, the mold was placed in a water bath or oil bath and foamed at a temperature of 100 ℃. Since the particles shrink due to an excessively high temperature, the surfaces of the particles are damaged, resulting in the above-mentioned foamed product having poor appearance and unsatisfactory size.
Example 4
Unlike example 1, in this example, in step 3, the mold was placed in a water bath or oil bath for a foaming time of 30 s. The foamed product has poor bonding strength because the particles are not completely combined by penetration.
Example 5
Example 1 in this example, the permeation amount of the supercritical fluid in step 2 was 25% by weight. The expansion degree of the foaming particles is too high, the density is relatively low, and the use requirement of foaming products cannot be met.
Example 6
Example 1 in this example, the permeation amount of the supercritical fluid in step 2 was 5% by weight. The expanded particles have a small degree of expansion and are not bonded together.
Example 7
Example 1 in this example, the difference is that, in step 2, the infiltration is carried out at a pressure of 0.5 Mpa. The foaming particles can hardly absorb physical foaming agent, and the foaming particles after pressure maintaining have no foaming tendency
Example 8
Example 1 in this example, the difference is that, in step 2, the pressure-holding infiltration was performed under a pressure of 3Mpa for 5 min. The foaming particles are obviously insufficient in absorbing physical foaming agents, and cannot be subjected to subsequent forming steps due to micro-foaming.
Example 9
Example 1 except that in this example, 0.3 wt% of a polyester chain extender and 0.3 wt% of calcium carbonate were used to modify amorphous polylactic acid. After pressure maintaining and foaming molding under standard conditions, the foamed product has insufficient mechanical strength, large density and insufficient surface smoothness.
The above-described embodiments are merely preferred examples of the present invention, and not intended to limit the scope of the invention, so that equivalent changes or modifications in the structure, features and principles of the invention described in the claims should be included in the claims.
Claims (10)
1. A foaming forming method of modified amorphous polylactic acid is characterized in that: the foam molding method comprises the following steps:
step 1, modifying amorphous polylactic acid by using a modification auxiliary agent, wherein the modification auxiliary agent is one or more of a chain extender and a nucleating agent;
step 2, placing the modified amorphous polylactic acid into an autoclave, and performing high-pressure permeation by using a supercritical fluid to infiltrate the modified amorphous polylactic acid by using the supercritical fluid so as to obtain pre-expanded beads;
and 3, placing the pre-foamed beads into a water bath or an oil bath, foaming the pre-foamed beads in a mold inside the water bath or the oil bath for 1-14 min at the temperature of 60-90 ℃, and cooling to obtain a molded foamed product.
2. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in the step 1, the chain extender is used for modifying the amorphous polylactic acid, or the chain extender and the nucleating agent are used for modifying the amorphous polylactic acid, and the adding amount of the chain extender is 1 wt% -1.5 wt%.
3. The method of claim 2, wherein the foaming molding of the modified amorphous polylactic acid is performed by: the chain extender is one or more of a polyester chain extender and an epoxy chain extender.
4. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: the nucleating agent is used for modifying the amorphous polylactic acid, or the chain extender and the nucleating agent are used for modifying the amorphous polylactic acid, and the addition amount of the nucleating agent is 1 wt% -2 wt%.
5. The method of claim 4, wherein the foaming molding of the modified amorphous polylactic acid is performed by: the nucleating agent is one or more of calcium carbonate, talcum powder, mica powder, argil, zinc oxide powder and titanium dioxide.
6. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in step 1, the modification of the amorphous polylactic acid specifically comprises the following steps:
step 1.1, mixing a modification auxiliary agent with polylactic acid to obtain a mixed raw material;
step 1.2, putting the raw materials into extrusion equipment, and extruding the raw materials through the extrusion equipment;
and step 1.3, cutting the raw materials to obtain the mixed long-strip blocky raw materials.
7. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in the step 2, pressure-maintaining infiltration is performed for 10-100 min under the pressure of 1-6 MPa.
8. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in step 2, the permeation amount of the supercritical fluid is 8% to 20% by weight.
9. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in step 2, the supercritical fluid is one of a carbon dioxide supercritical fluid and a nitrogen supercritical fluid.
10. The method of claim 1, wherein the foaming molding of the modified amorphous polylactic acid is performed by: in step 1, the method further comprises: putting the modified amorphous polylactic acid into a mould; in step 2, the method further comprises: placing the modified amorphous polylactic acid into a high-pressure kettle along with a mould; in step 3, the method further comprises: the mold is placed in a water bath or oil bath.
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| CN113146916A (en) * | 2021-03-17 | 2021-07-23 | 山东大学 | Polymer mould pressing foaming forming process based on gas presaturation |
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| US20100029793A1 (en) * | 2007-01-30 | 2010-02-04 | Michael Ralph Juergen Witt | Methods of manufacture of polylactic acid foams |
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