CN113214616B

CN113214616B - Low-odor biodegradable PLA alloy applied to food contact field and preparation method thereof

Info

Publication number: CN113214616B
Application number: CN202110658053.2A
Authority: CN
Inventors: 袁天楠; 王倩倩; 吴俊�; 李明哲
Original assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2022-07-12
Anticipated expiration: 2041-06-15
Also published as: CN113214616A

Abstract

The invention provides a low-odor biodegradable PLA alloy applicable to the field of food contact and a preparation method thereof. The method comprises the steps of firstly preparing vanilla extract, then adding porous aluminosilicate powder and dilute hydrochloric acid, modifying through the processes of co-heating, vacuum drying and the like to prepare essence modified porous silicon-aluminum, and finally preparing the low-odor biodegradable PLA alloy. The essence modified porous silicon-aluminum can emit vanilla flavor to cover the odor of the raw materials on one hand, and can adsorb peculiar smell micromolecules generated in the PLA processing process on the other hand, so that the PLA alloy achieves the effect of low odor. The prepared PLA alloy can be widely applied to the fields of food contact materials such as straws, lunch boxes, shopping bags and the like.

Description

Low-odor biodegradable PLA alloy applied to food contact field and preparation method thereof

Technical Field

The invention belongs to the field of food contact degradable materials, and particularly relates to a low-odor biodegradable PLA alloy applied to the field of food contact and a preparation method thereof.

Background

In recent years, various countries have issued plastic forbidding orders, and a strong plastic forbidding policy is put into force in China in various provinces and cities, so that biodegradable materials are more and more attracted attention, and the application fields of the biodegradable materials are continuously expanded, such as food contact materials, mulching films, film bags and the like.

The modified polylactic acid has good degradability and mechanical property, and is visible everywhere in daily life, such as milk tea straws, transfusion tools, cups, lunch boxes and the like. Because the modified polylactic acid is mostly applied to food contact materials, the defect of obvious peculiar smell of part of the modified polylactic acid is gradually revealed, and the peculiar smell cannot be accepted by the public, thereby limiting the market breakthrough of the modified polylactic acid material. Therefore, the modified PLA material with low odor can be prepared, and the application and market of the modified PLA material in the field of food contact materials can be expanded.

CN109627716A discloses a low-odor PLA alloy for 3D printing and a method for preparing the same, wherein low odor is achieved by coating a flame retardant mixture to reduce the release of late-stage odor substances, thereby reducing the odor of the material. But the odor is reduced by the coating adsorption principle, and is limited by the type of the filler, the processing technology and the application scene of the PLA. The food contact PLA alloy is also applied to hot drinks, the use temperature is sometimes higher, the coating adsorption effect is influenced, and food-grade fillers with the coating adsorption effect are not found for a while.

Therefore, the existing preparation method of the low-odor PLA alloy is not suitable for preparing low-odor PLA alloy materials for food contact, and a new odor control idea needs to be adopted to develop the low-odor biodegradable PLA alloy applied to the food contact field.

Disclosure of Invention

The invention aims to provide a low-odor biodegradable PLA alloy which can be applied to the field of food contact. By adding the special essence to modify the porous silicon aluminum, on one hand, pleasant vanilla flavor is emitted to cover and neutralize the original peculiar smell of the modified PLA alloy, and on the other hand, the modified porous silicon aluminum has an adsorption effect and can adsorb peculiar smell micromolecules in the processing or using process, so that the effect of low smell of the final product is achieved. And through modifying the porous silicon-aluminum, the compatibility with a matrix can be enhanced, the high-temperature resistance is realized, a certain slow release effect is realized, and the fragrance is kept for a long time.

In order to achieve the purpose, the invention adopts the following technical scheme:

a low-odor biodegradable PLA alloy for use in food contact applications, the PLA alloy comprising the following components in weight percent:

s1, PLA, 15% -45%, preferably 25% -35%;

s2, PBS, 35% -65%, preferably 45% -55%;

s3, mineral powder, 10% -30%, preferably 15% -25%;

s4, hydrolysis resistant agent, 0.05% -2%, preferably 0.1% -1%;

s5, a chain extender, 0.05% -2%, preferably 0.1% -0.8%;

s6, 0.01-0.2% of essence modified porous silicon aluminum, preferably 0.02-0.1%;

the essence modified porous silicon-aluminum is prepared from the following components:

s7, extracting vanilla;

s8, mixing porous aluminosilicate powder with vanilla extractive solution at a ratio of 5-35g/200mL, preferably 7-18g/200 mL;

s9, acid for adjusting the pH value to 1-6, preferably 4-5; the acid is volatile non-oxidizing acid, preferably dilute hydrochloric acid and hydrofluoric acid;

wherein the vanilla extract is prepared from the following components:

s10, vanilla pods;

s11, ethanol, the dosage is 1-10 times, preferably 7-9 times of the weight of the vanilla pods.

In the modification process of PLA, the odor of the PLA alloy can be improved by directly adding essence and porous silicon-aluminum, but the effect is not obvious, on one hand, the odor is generated due to the oxidative decomposition of essence micromolecules, on the other hand, a large number of essence micromolecules occupy the adsorption gaps of the porous silicon-aluminum, so that the adsorption effect of the porous silicon-aluminum is reduced, and finally, the odor is still obvious. According to the invention, the stable essence modified porous silicon aluminum is prepared firstly, so that the essence modified porous silicon aluminum has better compatibility and higher high temperature resistance in the process of blending with the PLA and other raw materials, the essence is prevented from being dispersed unevenly or decomposed at high temperature in the processing process, and the porous silicon aluminum has enough adsorption capacity on small molecules generated by processing, so that the prepared modified PLA alloy has lower smell.

In the invention, the PLA (polylactic acid) is one or more of ring-opening polymerization PLA and direct polycondensation PLA, preferably direct polycondensation PLA; preferably, the PLA has a melt index of 1-30g/10min (190 ℃, 2.16kg), preferably 3-15g/10min (190 ℃, 2.16 kg).

In the invention, the PBS (poly butylene succinate) is one or more of direct esterification PBS and ester exchange reaction PBS, preferably ester exchange reaction PBS; preferably, the PBS has a melt index of 10-30g/10min (190 ℃, 2.16kg), preferably 15-20g/10min (190 ℃, 2.16 kg).

In the invention, the mineral powder is one or more of talcum powder, calcium carbonate, wollastonite and mica, and calcium carbonate is preferred.

In the present invention, the hydrolysis resistant agent is one or more of a polymeric type and a monomeric type, and preferably a polymeric type hydrolysis resistant agent, for example, one or more of HY210, DSA10A, and K-1.

In the invention, the chain extender is one or more of ADR4468 and XY 437.

Another object of the present invention is to provide a method for preparing the low-odor biodegradable PLA alloy.

A preparation method for preparing the low-odor biodegradable PLA alloy, the method comprising the steps of:

A. mixing vanilla pods with ethanol, continuously heating and refluxing to prepare vanilla extract;

B. mixing porous aluminosilicate powder and vanilla extract, controlling system pH at 1-6 with acid, co-heating under reflux, and vacuum drying to obtain essence modified porous silica-alumina;

C. mixing PLA, PBS, mineral powder, an anti-hydrolysis agent, a chain extender and the essence modified porous silicon-aluminum, adding the mixture into a double-screw extruder, melting and extruding the mixture, cooling, cutting into granules and drying to obtain the PLA alloy.

In the invention, the heating temperature of the step A is 30-75 ℃, preferably 50-70 ℃, and the heating time is 8-20 hours, preferably 10-15 hours.

In the present invention, step B is carried out by controlling the pH to 1 to 6, preferably 4 to 5; heating at 40-70 deg.C, preferably 55-65 deg.C for 4-10 hr, preferably 6-8 hr; the vacuum drying temperature is 80-100 deg.C, and the drying time is 1-4 h.

In the invention, the raw materials in the step C are mixed by a high-speed mixer at the rotating speed of 20-100 rpm, preferably 30-80 rpm; the temperature is 20-50 ℃, and preferably 30-40 ℃; the mixing time is 3-10 min, preferably 5-7 min. The screw temperature of the double-screw extruder is 150-210 ℃, preferably 160-200 ℃; the rotation speed is 100-800rpm, preferably 200-500 rpm.

The PLA alloy prepared by the invention can be widely applied to the field of food contact materials such as straws, lunch boxes, shopping bags and the like.

Compared with the prior art, the invention has the following technical advantages:

1) by adding the essence modified porous silicon-aluminum modified PLA alloy, the overall smell of the PLA alloy is lower, the mechanical property of the PLA alloy is not reduced, the temperature resistance, precipitation performance and other performances of the PLA alloy can be improved surprisingly, the PLA alloy is applied to the field of food contact, and the PLA alloy is more friendly to consumers.

2) According to the invention, the stable essence modified porous silicon aluminum is prepared firstly, so that the essence modified porous silicon aluminum has better compatibility and higher high temperature resistance in the process of blending with the PLA and other raw materials, the essence is prevented from being dispersed unevenly or decomposed at high temperature in the processing process, and the porous silicon aluminum has enough adsorption capacity on small molecules generated by processing, so that the prepared modified PLA alloy has lower smell.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be illustrative of the invention and are not to be construed as limiting the scope of the invention.

In each of the examples and comparative examples, the main raw material sources were as follows:

other raw materials and reagents were obtained from commercial sources unless otherwise specified.

In each of the examples and comparative examples, the odor rating of the PLA alloy was tested according to Standard GB/T35773-2017 and the sample size was 600cm²The test condition is that the glass is placed for 24 hours at 23 ℃ in the dark; the samples were rated from low to high odor, 0-4; tensile strength, tensile modulus and elongation at break were tested according to standard ISO527-1: 2012; the flexural strength and flexural modulus are tested according to the standard ISO178: 2019; thermal changeThe shape temperature is tested according to the standard ISO306: 2013; the total migration was tested according to standard GB 31604.1-2015.

The processing equipment is as follows: a twin-screw extruder, koilong, model ZSK 26Mc 18, length-diameter ratio of 52, screw diameter of 26 cm; a film blowing machine, a model SCM 25, a length-diameter ratio of 30 and a screw diameter of 25cm, of Yangtze river machinery Co., Ltd, Zhang Jia gang City; an injection molding machine, Claus-Murphy, model KM130-380CX, length-diameter ratio of 20.2 and screw diameter of 35 mm.

The test equipment used was: a German Leifheit odor bottle with the specification of 1L; ZWICK-Z010TE universal tester; ZWICK-HIT25P pendulum impact instrument; CEAST-HV6M thermal deformation Vicat instrument; guangzhou west Tang Dynamo-electric-ERT-121B Total migration volume and non-volatile matter constant weight apparatus.

Example 1

(1) Preparing vanilla extract

Weighing 50g of vanilla pods, adding the vanilla pods into a flask, adding 450mL of ethanol, heating in a constant-temperature water bath, installing a reflux device, setting the temperature of the water bath at 70 ℃, and heating for 15 h; filtering and collecting clear extracting solution.

(2) Preparation of essence modified porous silicon-aluminum

Weighing 18g of porous aluminosilicate powder, adding into 200mL of the extracting solution, heating in a constant-temperature water bath, installing a reflux device, adjusting the pH to 4-5 with dilute hydrochloric acid, controlling the pH to be kept stable during the heating reaction, setting the temperature of the water bath to 65 ℃, heating for 8h, pouring the mixed solution into a vacuum drying tray, and performing vacuum drying at 100 ℃ for 4h to obtain the essence modified porous aluminosilicate.

(3) The essence modified porous silicon-aluminum and the formula components in the table 1 are used as raw materials, and the PLA alloy is prepared according to the following method by referring to the raw material dosage in the table 1:

a) firstly, respectively drying PLA and PBS pure materials in an electrothermal blowing drying oven for 4 hours at the temperature of 80 ℃.

b) Uniformly mixing PLA, PBS, mineral powder, an anti-hydrolysis agent, a chain extender and the essence modified porous silicon-aluminum in a high-speed mixer at the mixing speed of 90rpm for 7min at the mixing temperature of 40 ℃.

c) After mixing, adding the main feed of a double-screw extruder, and carrying out melt extrusion. The extrusion conditions were: the rotating speed of the screw is 300rpm, and the temperature of the screw is set from the feed opening to the machine head in a segmented mode as follows: 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 195 ℃.

d) And cooling the extruded material in a water tank of an extruder, pelletizing, and drying in a vacuum oven at 90 ℃ for 4 hours to obtain the PLA alloy.

Example 2

(1) Preparing vanilla extract

Weighing 50g of vanilla pods, adding the vanilla pods into a flask, adding 400mL of ethanol, heating in a constant-temperature water bath, installing a reflux device, setting the temperature of the water bath at 60 ℃, and heating for 12.5 hours; the clear extract was collected by filtration.

(2) Preparation of essence modified porous silicon-aluminum

Weighing 14g of porous aluminosilicate powder, adding into 200mL of the extracting solution, heating in a constant-temperature water bath, installing a reflux device, adjusting the pH to 4-5 with dilute hydrochloric acid, controlling the pH to be kept stable during the heating reaction, setting the temperature of the water bath to be 60 ℃, heating for reaction for 7h, pouring the mixed solution into a vacuum drying tray, and performing vacuum drying at 90 ℃ for 2h to obtain the essence modified porous aluminosilicate.

c) After mixing, adding the main feed of a double-screw extruder, and carrying out melt extrusion. The extrusion conditions were: the screw rotation speed is 280rpm, and the screw temperature is set from the feed opening to the machine head in a segmented mode as follows: 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 195 ℃ and 200 ℃.

Example 3

(1) Preparing vanilla extract

Weighing 50g of vanilla pods, adding the vanilla pods into a flask, adding 350mL of ethanol, heating in a constant-temperature water bath, installing a reflux device, setting the temperature of the water bath at 50 ℃, and heating for 18 h; filtering and collecting clear extracting solution.

(2) Preparation of essence modified porous silicon-aluminum

Weighing 7g of porous aluminosilicate powder, adding into 200mL of the extracting solution, heating in a constant-temperature water bath, installing a reflux device, adjusting the pH to 4-5 with dilute hydrochloric acid, controlling the pH to be kept stable during the heating reaction, setting the temperature of the water bath to be 55 ℃, heating for reaction for 6h, pouring the mixed solution into a vacuum drying tray, and drying in vacuum for 1h at 80 ℃ to obtain the essence modified porous aluminosilicate.

c) After mixing, adding the main feed of a double-screw extruder, and performing melt extrusion. The extrusion conditions were: the rotating speed of the screw is 300rpm, and the temperature of the screw is set from the feed opening to the machine head in a segmented mode as follows: 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 195 ℃ and 195 ℃.

Comparative example 1

The PLA alloy was prepared by the method of example 1 using commercially available vanilla as a raw material without modification, except that the varieties of vanilla are different in table 1.

Comparative example 2

The PLA alloy was prepared as in example 1, using commercially available porous silica-alumina as the raw material, without modification, except that the porous silica-alumina in table 1 was different in type.

Comparative example 3

The PLA alloy is prepared by using commercially available porous silicon-aluminum and vanilla essence as raw materials according to the method in the example 1 without modification, and the difference is only that the vanilla essence and the porous silicon-aluminum in the table 1 are different in type.

Comparative example 4

The PLA alloy was prepared as in example 1 without the addition of vanilla, except that no vanilla and porous silica-alumina were added.

The PLA alloy materials obtained in examples 1-3 and comparative examples 1-4 were blown into films in an extrusion film blowing machine, the screw temperature was set at 160-

The PLA alloy materials obtained in the examples 1-3 and the comparative examples 1-4 were injection molded in an injection molding machine at a temperature of 190 ℃ to form standard sample strips, and the mechanical properties and temperature resistance were tested, the test results are shown in Table 2.

TABLE 1 raw materials and amounts (Kg) used in examples 1-3(S1-S3) and comparative examples 1-4(D1-D4)

Raw material	S1	S2	S3	D1	D2	D3	D4
								LX175	31	-	-	31	31	31	31
LX575	-	45	21	-	-	-	-
								803S	48.1	-	53.1	48.1	48.1	48.1	48.1
FZ91	-	38.1	-	-	-	-	-
								Chain extender ADR4468	0.3	-	0.7	0.3	0.3	0.3	0.3
XY4347 chain extender	-	0.1	-	-	-	-	-
								KL5 calcium carbonate	20	-	24.24	20	20	20	20
CC2500 calcium carbonate	-	16.58	-	-	-	-	-
								HY210 hydrolysis resisting agent	0.5	0.2	0.9	0.5	0.5	0.5	0.5
Essence modified porous silicon-aluminum	0.1	0.02	0.06	-	-	-	-
								Porous silica-alumina	-	-	-	-	0.1	0.05	-
Vanilla essence	-	-	-	0.1	-	0.05	-

TABLE 2 PLA alloys of examples 1-3(S1-S3) and comparative examples 1-4(D1-D4) Performance test results

As can be seen from comparative examples 1-4 and example 1, the odor of the PLA alloy can be improved by directly adding essence and porous silica-alumina in the modification process of PLA, but the effect is not obvious. The stable essence modified porous silicon-aluminum is prepared firstly, so that the prepared modified PLA alloy has obviously lower odor. Meanwhile, the essence modified porous silicon-aluminum alloy maintains the mechanical property of the PLA alloy, improves the temperature resistance of the PLA alloy and greatly reduces the migration and precipitation amount of the PLA alloy. The PLA alloy is applied to the field of food contact, and the product is more friendly to consumers.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and additions can be made without departing from the method of the present invention, and these modifications and additions should also be regarded as the protection scope of the present invention.

Claims

1. A low-odor biodegradable PLA alloy applicable to the food contact field is characterized in that the PLA alloy comprises the following components in percentage by weight:

S1、PLA，15%-45%；

S2、PBS，35%-65%；

s3, 10% -30% of mineral powder;

s4, 0.05% -2% of an anti-hydrolysis agent;

s5, a chain extender, 0.05% -2%;

s6, 0.01-0.2% of essence modified porous silicon aluminum.

2. The PLA alloy of claim 1, wherein the PLA alloy comprises the following components in weight percent:

S1、PLA，25%-35%；

S2、PBS，45%-55%；

s3, 15% -25% of mineral powder;

s4, 0.1-1% of an anti-hydrolysis agent;

s5, a chain extender, 0.1% -0.8%;

s6, 0.02-0.1% of essence modified porous silicon aluminum.

3. The PLA alloy of claim 1 or 2, wherein the essence-modified porous silica-alumina is prepared by:

s7, extracting vanilla;

s8, mixing porous aluminosilicate powder and vanilla extract at a ratio of 5-35g/200 mL;

s9, and acid for adjusting the pH value to 1-6.

4. The PLA alloy of claim 3 wherein the acid is hydrochloric acid and/or hydrofluoric acid.

5. The PLA alloy of claim 3, wherein the vanilla extract is prepared by:

s10, vanilla pods;

s11, ethanol, the dosage of which is 1-10 times of the weight of the vanilla pods.

6. The PLA alloy of any of claims 1-2, wherein the PLA is one or more of a ring-opening polymerization PLA and a direct polycondensation PLA;

the PBS is one or more of direct esterification PBS and ester exchange reaction PBS.

7. PLA alloy according to claim 6, wherein the melt index of the PLA is from 1 to 30g/10min, the test conditions being: 2.16kg at 190 ℃;

the melt index of the PBS is 10-30g/10min, and the test conditions are as follows: 190 ℃ and 2.16 kg.

8. The PLA alloy of any of claims 1-2, wherein the mineral powder is one or more of talc, calcium carbonate, wollastonite, and mica;

the hydrolysis resistant agent is one or more of polymeric and monomeric;

the chain extender is one or more of ADR4468 and XY 437.

9. The PLA alloy of claim 8, wherein the hydrolysis resistant agent is one or more of HY210, DSA10A, and K-1.

10. A method of making the PLA alloy of any one of claims 1-9, comprising the steps of:

a) mixing vanilla pods with ethanol, continuously heating and refluxing to prepare vanilla extract;

b) mixing porous aluminosilicate powder and vanilla extract, controlling pH to 1-6 with acid, co-heating under reflux, and vacuum drying to obtain essence modified porous silica-alumina;

c) mixing PLA, PBS, mineral powder, an anti-hydrolysis agent, a chain extender and essence modified porous silicon-aluminum, adding the mixture into a double-screw extruder, melting and extruding the mixture, cooling the mixture, cutting the mixture into particles, and drying the particles to obtain the PLA alloy.

11. The method according to claim 10, wherein the heating temperature in step a) is 30-75 ℃ and the heating time is 8-20 hours.

12. The method according to claim 10, wherein the co-heating temperature in step b) is 40-70 ℃ and the co-heating time is 4-10 h; the vacuum drying temperature is 80-100 deg.C, and the drying time is 1-4 h.

13. The preparation method of claim 10, wherein the mixing in step c) is performed by a high speed mixer at 20-100 rpm at 20-50 ℃ for 3-10 min.

14. The method according to any one of claims 10-13, wherein the screw temperature of the twin-screw extruder in step c) is 150-.