CN111253721B - Transparent high-melt-strength polylactic acid and preparation method thereof - Google Patents
Transparent high-melt-strength polylactic acid and preparation method thereof Download PDFInfo
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- CN111253721B CN111253721B CN201910180112.2A CN201910180112A CN111253721B CN 111253721 B CN111253721 B CN 111253721B CN 201910180112 A CN201910180112 A CN 201910180112A CN 111253721 B CN111253721 B CN 111253721B
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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
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/14—Peroxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/02—Making granules by dividing preformed material
- B29B9/06—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
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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
- C08K5/00—Use of organic ingredients
- C08K5/49—Phosphorus-containing compounds
- C08K5/51—Phosphorus bound to oxygen
- C08K5/52—Phosphorus bound to oxygen only
- C08K5/524—Esters of phosphorous acids, e.g. of H3PO3
- C08K5/526—Esters of phosphorous acids, e.g. of H3PO3 with hydroxyaryl compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/10—Transparent films; Clear coatings; Transparent materials
Abstract
The transparent polylactic acid with high melt strength is characterized by being prepared from the following raw materials in parts by weight: 95.20 to 99.83 percent of polylactic acid; 0.10 to 2.00 percent of dicarbonate organic peroxide; 0.07-2.80% of phosphite ester antioxidant. The invention also provides a preparation method of the transparent high-melt-strength polylactic acid. According to the invention, a phosphite antioxidant is used for regulating and controlling a dicarbonate organic peroxide, and a polylactic acid is induced to generate a melting free radical reaction, so that a large amount of long-chain branched structures are endowed to the polylactic acid, thereby obviously improving the melt strength of the polylactic acid, simultaneously ensuring that the gel content of the polylactic acid is low, and avoiding the defect of fish eyes; on the basis of not sacrificing the existing advantages of polylactic acid and not generating new defects, the invention can solve the problem of poor melt strength of polylactic acid; the decomposition product of the dicarbonate organic peroxide is mainly carbon dioxide, so that the prepared transparent high-melt-strength polylactic acid is safe and nontoxic, and can be applied to products in contact with food.
Description
Technical Field
The invention relates to the technical field of high polymer materials, in particular to transparent polylactic acid with high melt strength and a preparation method thereof.
Background
In recent years, with the rapid development of electronic commerce (particularly, online shopping and take-out), the rapid development of disposable plastic products such as plastic express bags and the like is greatly promoted. However, the existing disposable plastic products have the characteristics of nondegradable property and high recovery cost, so that the wastes thereof cause severe white pollution and cause severe damage to the earth ecological environment, particularly the marine ecological system. Recently, there have been reports that plastic particles have entered the biological circulatory system and have appeared in human feces. In addition, most of the traditional polymer materials are derived from non-renewable petrochemical resources, which not only aggravates the problem of 'petroleum resource shortage', but also has no sustainable development. With the increasing enhancement of environmental awareness of people, a plurality of enterprises have already provided corresponding plastic banning orders, and international enterprises such as kendeki, mcdonald's worth, starbucks, wanhao and lijia have announced that traditional non-degradable disposable plastic products are gradually eliminated.
Among the degradable high molecular materials, polylactic acid (PLA) has the advantages of maximum yield, lowest price, optimal comprehensive mechanical property and renewable resource source. However, polylactic acid is a linear aliphatic polyester, and the melt strength is particularly low, so that the processing window is narrow and the melt stability is poor, so that the polylactic acid is difficult to meet the processing and forming modes of traditional foaming, thermoforming, bottle blowing, film blowing, spinning, extrusion forming and the like, and the application and popularization of polylactic acid products are greatly limited.
The existing technology for improving the melt strength of polylactic acid mainly comprises the steps of improving molecular weight, branching/crosslinking modification, nano modification and the like. Among them, increasing the molecular weight is mainly achieved by prolonging the polymerization time, which results in degradation of the polylactic acid and significant darkening of the color. The nano modification needs to treat the surface of the nano particles in advance, the production cost is high, and the technology is still in a laboratory stage. Branching/crosslinking modifications include melt reaction techniques and radiation crosslinking techniques. The high melt strength polylactic acid prepared by the existing reported branching/crosslinking modification technology contains a large amount of crosslinking substances, namely, gelation phenomenon, so that a transparent polylactic acid product has a large amount of gel points, namely, the defect of 'fish eyes', and the problems of hole breakage and fracture occur in the processes of thermoforming, bottle blowing, film blowing and spinning, and the problem of instability exists in the processes of foaming and extrusion molding. Therefore, there is a need for improvement of polylactic acid against the "fish eye" defect and the low melt strength defect of polylactic acid, so that the polylactic acid can be popularized in a large scale.
Disclosure of Invention
The invention aims to solve the technical problem of providing transparent polylactic acid with high melt strength and a preparation method thereof, wherein the transparent polylactic acid with high melt strength has low gel content and high melt strength, and can not generate the defect of fish eyes. The technical scheme is as follows:
the transparent polylactic acid with high melt strength is characterized by being prepared from the following raw materials in parts by weight: 95.20 to 99.83 percent of polylactic acid; 0.10 to 2.00 percent of dicarbonate organic peroxide; 0.07-2.80% of phosphite ester antioxidant.
The polylactic acid is preferably one or a combination of more of L-type polylactic acid, D-type polylactic acid and LD-mixed polylactic acid.
Preferably, the organic peroxide of the dicarbonate is one or a combination of more of di (2-ethylhexyl) peroxydicarbonate, di- (tetradecyl) peroxydicarbonate and di- (hexadecyl) peroxydicarbonate.
Preferably, the phosphite antioxidant is one or a combination of more of antioxidant 168, antioxidant 618 and antioxidant 626.
The phosphite ester antioxidant preferably has a mole number of phosphite ester molecules that is 1/3 of the mole number of the peroxy bond of the organic peroxide of the dicarbonate type.
Preferably, the transparent high-melt-strength polylactic acid is prepared from the following raw materials in parts by weight: 97.60 to 99.49 percent of polylactic acid; 0.30 to 1.00 percent of dicarbonate organic peroxide; 0.21 to 1.40 percent of phosphite ester antioxidant.
The invention also provides a preparation method of the transparent high-melt-strength polylactic acid, which is characterized by comprising the following steps:
(1) The following raw materials are prepared by weight: 95.20 to 99.83 percent of polylactic acid, 0.10 to 2.00 percent of dicarbonate organic peroxide and 0.07 to 2.80 percent of phosphite antioxidant;
(2) Drying polylactic acid at 100-120 deg.C for 30-90min to make the water content of polylactic acid less than 200ppm, and cooling to 20-30 deg.C;
(3) Adding a dicarbonate organic peroxide and a phosphite antioxidant into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material by a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
Preferably, the screw length-diameter ratio of the twin-screw extruder in the step (4) is 36. The screw of the double-screw extruder adopts a proper length-diameter ratio, so that the materials can be fully mixed, and the degradation of the materials caused by overlong heating time can be avoided.
The temperature of the twin-screw extruder in the above step (4) is preferably 180 to 210 ℃.
The transparent polylactic acid with high melt strength has the following advantages:
(1) According to the invention, a phosphite antioxidant is used for regulating and controlling a dicarbonate organic peroxide, and a polylactic acid is induced to generate a melting free radical reaction, so that a large amount of long-chain branched structures are endowed to the polylactic acid, thereby obviously improving the melt strength of the polylactic acid, simultaneously ensuring that the gel content of the polylactic acid is low, and avoiding the defect of fish eyes; on the basis of not sacrificing the existing advantages of polylactic acid and not generating new defects, the invention can solve the problem of poor strength of polylactic acid melt;
(2) The decomposition product of the dicarbonate organic peroxide is mainly carbon dioxide, so that the prepared transparent high-melt-strength polylactic acid is safe and nontoxic, and can be applied to products in contact with food;
(3) The invention is prepared by adopting the melt extrusion technology of a double-screw extruder, has the advantages of simple and convenient operation, high production efficiency, low processing cost and strong controllability, and can meet the requirement of industrial application.
Drawings
FIG. 1 is a plot of complex viscosity versus frequency for all polylactic acid disc samples in a specific example of the invention.
Detailed Description
Example 1
In this embodiment, the preparation method of the transparent high melt strength polylactic acid sequentially comprises the following steps:
(1) The following raw materials are prepared by weight: 99.82 percent of polylactic acid, 0.10 percent of peroxydicarbonate di- (tetradecyl) ester and 168.08 percent of antioxidant;
(2) Drying polylactic acid at 105 deg.C for 60min to make the water content of polylactic acid less than 200ppm, and cooling to 25 deg.C;
(3) Adding di- (tetradecyl) peroxydicarbonate and an antioxidant 168 into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material by a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
The screw length-diameter ratio of the twin-screw extruder in the step (4) is 48.
The temperature of the twin-screw extruder in the above step (4) was 190 ℃.
Example 2
In this embodiment, the preparation method of the transparent high melt strength polylactic acid sequentially comprises the following steps:
(1) The following raw materials are prepared by weight: 99.47 percent of polylactic acid, 0.30 percent of peroxydicarbonate di- (tetradecyl) ester and 168.23 percent of antioxidant;
(2) Drying polylactic acid at 100 deg.C for 30min to make the water content of polylactic acid less than 200ppm, and cooling to 20 deg.C;
(3) Adding di- (tetradecyl) peroxydicarbonate and an antioxidant 168 into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
The screw length-diameter ratio of the twin-screw extruder in the step (4) is 36.
The temperature of the twin-screw extruder in the above step (4) was 180 ℃.
Example 3
In this embodiment, the preparation method of the transparent high melt strength polylactic acid sequentially comprises the following steps:
(1) The following raw materials are prepared by weight: 98.95 percent of polylactic acid, 0.60 percent of peroxydicarbonate di- (tetradecyl) ester and 168.45 percent of antioxidant;
(2) Drying polylactic acid at 120 deg.C for 90min to make the water content of polylactic acid less than 200ppm, and cooling to 30 deg.C;
(3) Adding peroxydicarbonate di- (tetradecyl) ester and antioxidant 168 into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
The screw length-diameter ratio of the twin-screw extruder in the step (4) is 52.
The temperature of the twin-screw extruder in the above step (4) was 210 ℃.
Example 4
In this embodiment, the preparation method of the transparent high melt strength polylactic acid sequentially comprises the following steps:
(1) The following raw materials are prepared by weight: 98.24 percent of polylactic acid, 1.00 percent of peroxydicarbonate di- (tetradecyl) ester and 168.76 percent of antioxidant;
(2) Drying polylactic acid at 110 deg.C for 80min to make the water content of polylactic acid less than 200ppm, and cooling to 30 deg.C;
(3) Adding peroxydicarbonate di- (tetradecyl) ester and antioxidant 168 into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
The screw length-diameter ratio of the twin-screw extruder in the above step (4) was 48.
The temperature of the twin-screw extruder in the above step (4) was 200 ℃.
Comparative example 1
The preparation method of the high melt strength polylactic acid in this comparative example is different from that of example 1 in that:
(1) The following raw materials are prepared by weight: 99.50 percent of polylactic acid and 168.50 percent of antioxidant;
(2) Drying polylactic acid at 105 deg.C for 60min to make the water content of polylactic acid less than 200ppm, and cooling to 25 deg.C;
(3) Adding an antioxidant 168 into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular polylactic acid.
Comparative example 2
The preparation method of the high melt strength polylactic acid in the present comparative example is different from that of example 1 in that:
(1) The following raw materials are prepared by weight: 99.40 percent of polylactic acid and 0.60 percent of peroxydicarbonate di- (tetradecyl) ester;
(2) Drying polylactic acid at 120 deg.C for 90min to make the water content of polylactic acid less than 200ppm, and cooling to 30 deg.C;
(3) Adding peroxydicarbonate di- (tetradecyl) ester into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular polylactic acid.
The properties of the high melt strength polylactic acid obtained in the above examples 1 to 4 and comparative examples 1 to 2 were measured, wherein:
(1) And (3) rheological property testing:
the polylactic acid particles obtained in examples 1 to 4 and comparative examples 1 to 2 were press-molded into a circular piece having a diameter of 25mm and a thickness of 2mm by using a vacuum plate press. The complex viscosity of all polylactic acid disc samples was obtained by dynamic frequency scanning of the polylactic acid discs under nitrogen protection using an ARES rheometer (ARES 4400-94, TA, USA), and the test results are shown in FIG. 1.
As can be seen from the above test results, the complex viscosities of examples 1 to 4 and comparative example 2 were significantly improved relative to comparative example 1, indicating that the polylactic acids of examples 1 to 4 and comparative example 2 have characteristics of high melt strength, and it was found that the polylactic acid discs of examples 1 to 4 did not exhibit any "fish eye" defect, while the polylactic acid discs of comparative example 2 exhibited a large amount of "fish eye" defect.
(2) And (3) testing the gel content:
polylactic acid samples obtained in examples 1-4 and comparative examples 1-2 were weighed to 0.5g, and recorded as m 0 Adding 50ml of chloroform and stirring for 12 hours; then, a 120-mesh sieve (sieve weight m) was used 1 ) Filtering for 12h; next, the mesh was placed in 80 o C, drying in a vacuum oven for 12 hours; finally, the weight of the screen at that time is weighed as m 2 . Wherein the precision of the electronic scale is 0.01mg. According to the following formula:
gel (%) of the polylactic acids prepared in examples 1 to 4 and comparative examples 1 to 2 were obtained, and the test results are shown in the following table 1.
Table 1: evaluation results (gel content) of the products of examples and comparative examples
| Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | Comparative example 2 | |
| gel(%) | 0.6 | 1.3 | 2.6 | 4.8 | 0 | 32.6 |
As can be seen from the above test results, the gel content of the transparent high melt strength polylactic acid prepared in examples 1 to 4 was only 4.8% at the maximum, whereas the gel content of comparative example 2 was as high as 32.6%, and thus it was found that the gel content of the transparent high melt strength polylactic acid prepared in examples 1 to 4 was low.
The technology disclosed by the patent is not only limited to the preparation of the transparent high-melt-strength polylactic acid, but also is suitable for preparing other high-melt-strength polyester polymer materials, in particular degradable polymer materials. The embodiments described above are presented to facilitate one of ordinary skill in the art to understand and practice the present invention. Those skilled in the art can apply the above embodiments to other fields without inventive modifications, so the present invention is not limited to the above embodiments, and those skilled in the art can make improvements and modifications within the scope of the present invention.
Claims (9)
1. The transparent polylactic acid with high melt strength is characterized by being prepared from the following raw materials in parts by weight: 95.20 to 99.83 percent of polylactic acid; 0.10 to 2.00 percent of dicarbonate organic peroxide; 0.07-2.80% of phosphite ester antioxidant.
2. The transparent high melt strength polylactic acid according to claim 1, wherein: the polylactic acid is one or the combination of more of L-type polylactic acid, D-type polylactic acid and LD mixed polylactic acid.
3. The transparent high melt strength polylactic acid according to claim 1, wherein: the organic peroxide of the dicarbonate is one or the combination of more of di (2-ethylhexyl) peroxydicarbonate, ditetradecyl peroxydicarbonate and dicetyl peroxydicarbonate.
4. The transparent high melt strength polylactic acid according to claim 1, wherein: the phosphite antioxidant is one or the combination of more of antioxidant 168, antioxidant 618 and antioxidant 626.
5. The transparent high melt strength polylactic acid according to claim 1, wherein: the phosphite ester molecular number of the phosphite ester antioxidant is 1/3 of the peroxy bond mol number of the dicarbonate organic peroxide.
6. The transparent polylactic acid with high melt strength as claimed in claim 1, which is prepared from the following raw materials in parts by weight: 97.60 to 99.49 percent of polylactic acid; 0.30 to 1.00 percent of dicarbonate organic peroxide; 0.21 to 1.40 percent of phosphite ester antioxidant.
7. A preparation method of transparent polylactic acid with high melt strength is characterized by comprising the following steps:
(1) The following raw materials are prepared by weight: 95.20 to 99.83 percent of polylactic acid, 0.10 to 2.00 percent of dicarbonate organic peroxide and 0.07 to 2.80 percent of phosphite antioxidant;
(2) Drying polylactic acid at 100-120 deg.C for 30-90min to make the water content of polylactic acid less than 200ppm, and cooling to 20-30 deg.C;
(3) Adding a dicarbonate organic peroxide and a phosphite antioxidant into polylactic acid, and uniformly mixing to obtain a mixed material;
(4) And melting and extruding the mixed material through a double-screw extruder, and bracing, air cooling and granulating the material extruded by the double-screw extruder to obtain granular transparent high-melt-strength polylactic acid.
8. The method for preparing the transparent high melt strength polylactic acid according to claim 7, wherein: the screw length-diameter ratio of the twin-screw extruder in the step (4) is 36-52.
9. The method for preparing the transparent high melt strength polylactic acid according to claim 7, wherein: the temperature of the twin-screw extruder in the step (4) is 180-210 ℃.
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