HK40083945B - Polyhydroxyalkanoate composition containing polybasic acid, and polyhydroxyalkanoate molded article - Google Patents

Description

Polyhydroxyalkanoate composition containing polybasic acid and molded article of polyhydroxyalkanoate

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a polyhydroxy alkanoate composition containing polybasic acid and a polyhydroxy alkanoate forming body.

Background

Polyhydroxyalkanoates (PHAs) are intracellular polyhydroxyalkanoates synthesized by many microorganisms, and are natural high molecular biological materials. Most of the monomers of the polyhydroxyalkanoate are 3-hydroxy fatty acids with the chain length of 3-14 carbon atoms, the side chain R of the polyhydroxyalkanoate is a highly variable saturated or unsaturated, straight chain or branched chain, aliphatic or aromatic group, and the diversity of the composition structure brings about the diversification of the performance, so that the polyhydroxyalkanoate has obvious advantages in application. Meanwhile, polyhydroxyalkanoate is a bio-based polymer that is biodegradable in a marine environment, can solve environmental problems caused by waste plastics, and has excellent biocompatibility and mechanical properties, and thus, polyhydroxyalkanoate can be processed into various molded bodies, such as films, straws, tableware, and the like.

Molecular weight is the most important factor affecting the properties of polyhydroxyalkanoates. Because the polyhydroxyalkanoate has poor thermal stability, the polyhydroxyalkanoate has high thermal degradation degree in the process of preparing various molded bodies by adopting thermoplastic processing, so that the molecular weight of the polyhydroxyalkanoate is greatly reduced, and the various prepared molded bodies have poor performance, especially toughness. For example: compared with other types of polyester, the film forming body prepared by using polyhydroxyalkanoate as a raw material and adopting film blowing processing has the problems of obvious reduction of right-angle tearing performance, obvious reduction of elongation at break and the like. In addition, the high degree of thermal degradation also reduces the processing stability of the polyhydroxyalkanoates.

In the related art, in order to reduce the influence of the thermal degradation degree of polyhydroxyalkanoate in the processing process on the molecular weight and the processing stability of polyhydroxyalkanoate, some additives having a crosslinking effect, such as a chain extender and an organic peroxide, are often added to polyhydroxyalkanoate to crosslink molecules, so as to increase the molecular weight and reduce the influence of thermal degradation on the molecular weight. Or a certain micromolecule or polymer with toughening effect is added to offset the defects of toughness reduction and the like, and the processing stability is improved.

However, in order to solve the above problems, the peroxide, the compound having an epoxy functional group, or the cross-linking agent having at least two active double bonds used in the related art may easily react with an acidic substance, an antioxidant auxiliary, or the like due to high chemical activity, thereby causing a large storage risk and a safety hazard, and the reaction is difficult to quantitatively control due to high reactivity. Therefore, it is necessary to develop a safe and effective assistant to reduce the influence of thermal degradation of polyhydroxyalkanoate on molecular weight during thermal processing, improve the toughness of the molded article, and improve the product performance.

Disclosure of Invention

The invention provides a polyhydroxyalkanoate composition containing polybasic acid and a polyhydroxyalkanoate forming body, which are used for solving the defects that the existing polyhydroxyalkanoate has poor heat stability, the thermal degradation degree is large, the molecular weight is greatly reduced, the performance of various prepared forming bodies is poor and the like in the process of preparing various forming bodies by thermoplastic processing; and the polyhydroxyalkanoate and the polybasic acid compound are combined, so that the toughening effect can be achieved, the molecular weight of a forming body can be improved, the melt flow rate can be reduced, and the influence of thermal degradation of the polyhydroxyalkanoate on the performance of the forming body in the process of preparing various forming bodies through thermoplastic processing can be reduced to a certain extent.

In a first aspect, the present invention provides a polyhydroxyalkanoate composition comprising a polyhydroxyalkanoate and a polyacid compound.

In the scheme, the polyhydroxyalkanoate composition provided by the invention comprises polyhydroxyalkanoate and a polybasic acid compound, wherein the polybasic acid compound can play a toughening effect, can improve the molecular weight of a forming body, reduce the melt flow rate, and reduce the influence of thermal degradation of the polyhydroxyalkanoate on the performance of the forming body in the process of preparing various forming bodies through thermoplastic processing to a certain extent. The polybasic acid compound is one or more than one polybasic acid, and the polybasic acid refers to an acid which can generate two or more than two hydrogen ions after one acid molecule is ionized, or a compound with two or more than two terminal carboxyl groups. The acid in the polybasic acid can generate esterification reaction with the hydroxyl at the tail end of the polyhydroxyalkanoate, so that intermolecular chain extension and molecular chain extension are realized, the molecular weight of the molded body is improved, the problem of reduction of the molecular weight of the polyhydroxyalkanoate caused by large thermal degradation degree is solved, and the toughness of the molded body is improved.

According to the polyhydroxyalkanoate composition provided by the invention, the addition amount of the polybasic acid type compound is 0.01-20% of the mass of the polyhydroxyalkanoate.

Alternatively, the amount of the polybasic acid compound added may be 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 5%, 8%, 10%, 15%, 20% or the like based on the mass of the polyhydroxyalkanoate, and may be other values within the above range, which is not limited herein.

Preferably, the addition amount of the polybasic acid compound is 0.01-5% of the mass of the polyhydroxyalkanoate. Further, the addition amount of the polybasic acid compound is 0.05-5% of the mass of the polyhydroxyalkanoate.

More preferably, the addition amount of the polybasic acid compound is 0.05-2.5% of the mass of the polyhydroxyalkanoate.

By controlling the amount of the polybasic acid compound to be added within this reasonable range, the molded article obtained can be processed with better properties.

According to the polyhydroxyalkanoate composition provided by the present invention, the polybasic acid type compound is preferably an organic polybasic acid type compound, and the polybasic acid type compound is an organic acid type compound represented by a general formula R '(COOH) n, wherein R' is represented by: a hydrocarbon group having 2 to 30 carbon atoms, or a group composed of one or more of an aryl group, an epoxy group, an ether bond, a hydroxyl group, and a hydrocarbon group having 2 to 30 carbon atoms; n is an integer of 2 or more.

When R' is a hydrocarbon group containing 2-30 carbon atoms, the alkyl, alkenyl or alkynyl containing 2-30 carbon atoms can be used; r' can be alkyl with 2-5 carbon atoms, alkyl with 5-10 carbon atoms, alkyl with 10-20 carbon atoms or alkyl with 20-30 carbon atoms; specific non-limiting examples are ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, triacontyl and the like.

When R' is represented as: when the group is a combination of one or more of an aryl group, an epoxy group, an ether bond, a hydroxyl group and a hydrocarbon group having 2 to 30 carbon atoms, R' may be a combination of the above hydrocarbon group having 2 to 30 carbon atoms and an aryl group, a combination of the above hydrocarbon group having 2 to 30 carbon atoms and a hydroxyl group, a combination of the above hydrocarbon group having 2 to 30 carbon atoms and an ether bond, or the like. When the composition of the organic polyacid containing the above groups and the polyhydroxyalkanoate is used, the combination scheme of maintaining the molecular weight of the polyhydroxyalkanoate and reducing the melt index can be satisfied, and all the combinations are within the scope of the present application.

Further, when n is 2 or 3, the polybasic acid compounds comprise organic dibasic acid compounds and/or organic tribasic acid compounds. Further, the polybasic acid compound may be a saturated dibasic acid, an unsaturated dibasic acid, a saturated tribasic acid, or an unsaturated tribasic acid.

Preferably, the polybasic acid compound is a dibasic acid compound.

Unlike fatty acids having an aliphatic hydrocarbon chain with one carboxyl group at one end, dibasic acids refer to acids that produce two hydrogen ions upon ionization of one acid molecule, or compounds having two terminal carboxyl groups, or compounds represented by the general formula HOOC-R' -COOH. The tribasic acid refers to an acid which generates three hydrogen ions after ionization of one acid molecule, or a compound having three terminal carboxyl groups, or a molecule represented by the general formula R' (COOH) ₃ The compound shown in the specification. Generally, when the tribasic acid or other polybasic acids are used, the molecular weight can be increased and the melt index can be reduced as compared with the dibasic acids, but the molecular chain movement is influenced due to the large degree of crosslinking, the elongation at break is not increased, and the notch impact strength is not increased. The dibasic acid compound is added into the polyhydroxyalkanoate as the polybasic acid compound, and the molecular weight of the dibasic acid compound is higher than that of polyhydroxyalkanoate without any addition agent in the process of preparing various molded bodies by thermoplastic processing, and the Melt Flow Rate (MFR) of a particle molded body is lower, so that the performance of the prepared molded body is improved to a certain extent, especially the toughness, the notch impact strength of an injection molded body is higher, the right-angle tear strength and the elongation at break of a film molded body are higher, and the overall performance of the molded body is improved. Meanwhile, in the processing process of various molded bodies, the proper crosslinking degree can be kept, the movement of molecular chains is not influenced, and the processing is more stable.

Certainly, in the scheme, the polybasic acid compound also includes other types of polybasic acids, such as organic tetrabasic acids like ethylenediamine tetraacetic acid and pyromellitic acid, and inorganic polybasic acids like phosphoric acid, sulfuric acid, sulfurous acid and carbonic acid, as long as the acid in the polybasic acid can perform an esterification reaction with the hydroxyl at the tail end of the polyhydroxyalkanoate, so that intermolecular chain extension is realized, and the molecular chain is prolonged; therefore, the same effect as that of these types of polybasic acids can be obtained by increasing the molecular weight of the molded article, thereby making it possible to offset the problem of lowering of the molecular weight of the polyhydroxyalkanoate due to a large degree of thermal degradation and improve the toughness of the molded article. It was found that the inorganic polybasic acid combined with polyhydroxyalkanoate to prepare a molded article can increase the weight average molecular weight of the molded article, but the decrease of the melt flow rate of the molded article is not significant, and the tensile strength, elongation at break and notched impact strength are all low, and it is apparent that the inorganic acid does not have the similar effect as the organic polybasic acid. When an organic polybasic acid is used as the polybasic acid compound and the polyhydroxyalkanoate is combined to prepare a molded article, the problem of molecular weight reduction caused by thermal degradation can be solved as a whole, but the effects of organic acids with different carbon chain lengths are slightly different.

Further, the organic polybasic acid may be a compound having a hydroxyl group in the R' molecular structure, and the polybasic acid compound may be a hydroxyl group-containing polybasic acid compound such as tartaric acid (also referred to as 2, 3-dihydroxysuccinic acid), and L-tartaric acid (levo-tartrate), D-tartaric acid (dextro-tartrate), MESO-tartaric acid (MESO-tartrate), DL-tartaric acid (racemic modification), and the like may be selected depending on the structure. Of course, the scheme is not limited to that R' is polybasic acid containing two hydroxyl groups, and also can be polybasic acid containing more than two hydroxyl groups, such as tetrahydroxysuccinic acid and the like. Also, the polybasic acid having other groups is not limited, and examples thereof include polybasic acid compounds wherein R' is an ether bond, an ester bond, an amino group, or the like.

The organic dibasic acid is a compound represented by a general formula HOOC-R' -COOH, the organic tribasic acid is a compound containing three carboxyl groups in a molecular structure, and the terminal carboxyl groups in the molecular structures of the organic dibasic acid and the organic tribasic acid and the hydroxyl groups at the terminal of the polyhydroxyalkanoate are subjected to esterification reaction, so that intermolecular chain extension is facilitated, the molecular chain is further prolonged, and a more effective toughening effect can be achieved. Compared with organic tribasic acid, the organic dibasic acid as the polybasic acid compound can effectively improve the weight average molecular weight of the formed body, and can effectively improve the mechanical properties of the formed body, such as elongation at break, notch impact strength and the like, so that the overall performance of the formed body can be effectively improved.

According to the polyhydroxyalkanoate composition provided by the invention, the polybasic acid compound comprises an organic saturated dibasic acid, an unsaturated dibasic acid, and/or an organic saturated tribasic acid, an unsaturated tribasic acid, and/or a hydroxyl polybasic acid. R' in the polybasic acid-series compound is an unsaturated aryl group, a double bond-or triple bond-containing hydrocarbon group, and preferable unsaturated polybasic acid-series compounds include: glutaconic acid, 4-diphenylethylene dicarboxylic acid, terephthalic acid, and the like. The research shows that compared with the molded body prepared by adopting unsaturated polybasic acid as the polybasic acid compound and organic saturated polybasic acid as the polybasic acid compound, the saturated polybasic acid compound can effectively reduce the melt flow rate of the molded body and effectively improve the elongation at break of the molded body, thereby effectively improving the overall performance of the molded body. According to the polyhydroxyalkanoate composition provided by the invention, the polybasic acid compound is selected from one or more of oxalic acid, malonic acid, succinic acid, tartaric acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecane diacid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, tricosanedioic acid, tetracosane diacid, pentacosane diacid, hexacosane diacid, heptacosanedioic acid and 1,3, 5-tricarboxypentane.

By specially limiting the types of the organic dibasic acids, the formed body prepared by the polyhydroxyalkanoate composition has the advantages of good toughness, good processing stability, good mechanical property and the like, and the overall performance of the formed body is improved, so that the formed body has wider application capability. In addition, the organic dibasic acid selected by the invention is easy to store, and the difficulty of quantitative control reaction is not large.

The experimental result shows that the integral performance of the formed body prepared from the polyhydroxyalkanoate composition obtained by selecting the organic saturated dibasic acid as the polybasic acid compound is better than that of the unsaturated dibasic acid. Further, in order to secure the comprehensive properties of the molded body, according to the polyhydroxyalkanoate composition provided by the present invention, the polybasic acid type compound is selected from one or more of oxalic acid, malonic acid, succinic acid, tartaric acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, tricosanedioic acid, tetracosanedioic acid, pentacosanedioic acid, hexacosanedioic acid, heptacosanedioic acid.

The research on the saturated organic diacid compound for improving the thermal degradation of the polyhydroxyalkanoate finds that various saturated organic diacids have certain effects, and preferably, the polybasic acid compound comprises one or more of succinic acid, tartaric acid, glutaric acid, adipic acid, dodecanedioic acid and hexadecanedioic acid. The tartaric acid is selected from DL-tartaric acid, L-tartaric acid, D-tartaric acid, and MESO-tartaric acid.

According to the polyhydroxyalkanoate composition provided by the invention, the polyhydroxyalkanoate can be a single polymer or a composition of two or more polymers. Wherein the polymerized monomer of each polymer may be one or more (i.e., the structural unit in the polymer is one or more).

According to the present invention, there is provided a polyhydroxyalkanoate composition, which is a polymer comprising a repeating unit represented by the following general formula (1):

[CHR(CH ₂ )mCOO](1)

in the general formula (1), R represents CpH ₂ And p +1, wherein p represents an integer of 1 to 15, preferably an integer of 1 to 10, and more preferably an integer of 1 to 8. Examples of R include: a straight-chain or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a hexyl group.

m =1,2 or 3, and when m =1, the general formula (1) represents a 3-hydroxyalkanoate structural unit, when m =2, the general formula (1) represents a 4-hydroxyalkanoate structural unit, and when m =3, the general formula (1) represents a 5-hydroxyalkanoate structural unit. Among these, 3-hydroxyalkanoate structural units and 4-hydroxyalkanoate structural units are common, and examples thereof include a 3-hydroxybutyrate structural unit (hereinafter, may be referred to as 3 HB) and a 4-hydroxybutyrate structural unit (hereinafter, may be referred to as 4 HB).

According to the present invention there is provided a polyhydroxyalkanoate composition, comprising at least one poly (3-hydroxyalkanoate); the poly (3-hydroxyalkanoate) comprises only 3-hydroxybutyrate structural units, or comprises 3-hydroxybutyrate structural units and other hydroxyalkanoate structural units;

the other hydroxyalkanoate structural units comprise one or more of 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonanoate, 3-hydroxydecanoate, 3-hydroxyundecanoate, or 4-hydroxybutyrate; preferably, the other hydroxyalkanoate structural unit is 3-hydroxyhexanoate.

The polyhydroxyalkanoate composition provided in accordance with the present invention, the poly (3-hydroxyalkanoate) is selected from one or more of poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxypropionate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly (3-hydroxybutyrate-co-3-hydroxyheptanoate), poly (3-hydroxybutyrate-co-3-hydroxyoctanoate), poly (3-hydroxybutyrate-co-3-hydroxynonanoate), poly (3-hydroxybutyrate-co-3-hydroxydecanoate), poly (3-hydroxybutyrate-co-3-hydroxyundecanoate), poly (3-hydroxybutyrate-co-4-hydroxybutyrate);

preferably, the poly (3-hydroxyalkanoate) is selected from poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).

The method for producing the polyhydroxyalkanoate of the present invention is not particularly limited, and may be a method for producing the polyhydroxyalkanoate by chemical synthesis, or a method for producing the polyhydroxyalkanoate by a microorganism.

It has been found that the ratio of the structural monomer in the polyhydroxyalkanoate in the composition does not depend on the polybasic acid compound of the present invention. The polyhydroxyalkanoates according to the present invention are particularly preferably polyhydroxyalkanoates produced by microorganisms in which all of the 3-hydroxyalkanoate structural units are contained in the form of (R) 3-hydroxyalkanoate structural units. Wherein the poly (3-hydroxyalkanoate) comprises a copolymer of a 3-hydroxybutyrate structural unit and other structural units, and the average content ratio of the 3-hydroxybutyrate structural unit to the other structural units in the poly (3-hydroxyalkanoate) is 50/50 to 99/1 (mol%/mol%); the polybasic acid compound provided by the invention has a more obvious crystallization promoting effect on the preferable 80/20-94/6 (mol%/mol%); when the starting material of the polyhydroxyalkanoate is a mixture of two or more polyhydroxyalkanoates, the average content ratio refers to the molar ratio of the monomers contained in the entire mixture. Within the preferable range, the secondary molding difficulty and the processing efficiency can be both considered.

In practice, the person skilled in the art may add additives and other auxiliaries to the polyhydroxyalkanoate composition according to the production needs of the shaped body, without inhibiting the effects of the present invention. The additives may include organic or inorganic materials such as nucleating agents, plasticizers, toughening agents, reinforcing agents, crosslinking agents, chain extenders, lubricants, fillers, and the like. The organic or inorganic materials may be used alone or in combination of two or more. The amount of the additive may be adjusted according to production requirements, and the present invention is not particularly limited thereto.

The polyhydroxyalkanoate composition provided by the invention further comprises a nucleating agent, and the addition amount of the nucleating agent is 0.1% -10% of the polyhydroxyalkanoate composition; the nucleating agent comprises an auxiliary agent which plays a nucleating role in the field, such as a common inorganic nucleating agent, and comprises one or more of calcium carbonate, talcum powder, titanium dioxide, uracil, galactitol, zirconium hydrogen phosphate, amide compounds and boron nitride; of course, organic nucleating agents having a nucleating effect are also included, including, but not limited to, acid-based, alcohol-based nucleating agents, and the like.

The time required for the polyhydroxyalkanoate to not block can be reduced by adding a nucleating agent to the polyhydroxyalkanoate composition, thereby improving processing efficiency. Too high an amount of nucleating agent may reduce the mechanical properties of the polyhydroxyalkanoate.

In a second aspect, the present invention also provides a polyhydroxyalkanoate molded body comprising the polyhydroxyalkanoate composition described above.

The polyhydroxyalkanoate forming body obtained by the invention has the advantages of good processing stability and good mechanical property, thereby having wider application scenes. The shaped bodies according to the invention can comprise various forms, such as films, fibers, straws, plates, pellets and the like.

In a third aspect, the present invention also provides a method for preparing the above-mentioned polyhydroxyalkanoate molded body, comprising the steps of:

heating the polyhydroxyalkanoate composition at a first temperature, melting, and cooling at a second temperature for molding;

the first temperature is 10-60 ℃ higher than the melting point of the polyhydroxyalkanoate;

the second temperature is higher than the glass transition temperature of the polyhydroxyalkanoate molded body and lower than the melting point of the polyhydroxyalkanoate molded body; preferably, the second temperature is 30 ℃ or more higher than the glass transition temperature of the polyhydroxyalkanoate molded body and 20 ℃ or less lower than the melting point of the polyhydroxyalkanoate molded body.

In the preparation method, the polyhydroxyalkanoate composition is heated and melted at a first temperature, and then cooled and formed at a second temperature. The research of the invention finds that the lower the first temperature is, the shorter the time for the molded body not to be adhered in the cooling molding stage is, but the higher the first temperature is, the higher the fluidity of the polyhydroxyalkanoate is, and the molding is more facilitated. Comprehensively considering, in the heating and melting stage, the first temperature of the system is controlled to be 10-60 ℃ higher than the melting point of the polyhydroxyalkanoate. It has also been found that the second temperature influences the length of time it takes for the polyhydroxyalkanoate molded body to reach a non-blocking state, and that numerous tests have verified that the temperature of the system during the cooling molding stage lies between the glass transition temperature and the melting point temperature of the molded body obtained, preferably above 30 ℃ and below 20 ℃ above the glass transition temperature of the molded body obtained.

Meanwhile, the molding mode of the invention is divided into a thermoplastic processing molding mode and a non-thermoplastic processing molding mode; the thermoplastic processing and forming mode comprises extrusion forming, injection molding, calendaring forming, tape casting forming, blow molding forming, biaxial stretching forming and the like; the non-thermoplastic processing and forming mode comprises solution casting and the like. The thermoplastic forming mode is preferred.

The prior polyhydroxyalkanoate resin has the following problems in the preparation process: the weight average molecular weight of the molded body is reduced from 50 ten thousand to 32 ten thousand due to the thermal degradation, the melt flow rate is higher by 7.42 g/10min, and the breaking elongation is only 11%. To solve the problem, the invention provides a polyhydroxyalkanoate composition containing a polybasic acid compound to prepare a molded body, which can effectively reduce the thermal degradation, maintain the molecular weight of the molded body at 48 ten thousand or more, reduce the melt flow rate to 1.14 g/10min or less, and improve the elongation at break to 153% or more. The influence of thermal degradation of the polyhydroxyalkanoate on the performance of the formed body in the process of preparing various formed bodies through thermoplastic processing can be reduced to a certain degree, and the toughening effect is further achieved.

The polybasic acid compound is one or more than one, the carboxylic acid group end in the polybasic acid can generate esterification reaction with the hydroxyl at the tail end of the polyhydroxyalkanoate, so that intermolecular chain extension is realized, the molecular chain is prolonged, the molecular weight of the formed body is improved, the problem of the reduction of the molecular weight of the polyhydroxyalkanoate caused by large thermal degradation degree is solved, the prepared formed body has lower melt flow rate, higher tensile strength, elongation at break and notch impact strength, and the toughness of the formed body is further improved.

The polybasic acid compound in the polyhydroxyalkanoate composition is simple and convenient to use, can be used as an additive to be blended and compounded with polyhydroxyalkanoate, does not need redundant preparation methods and steps, and reduces the production cost.

Different from functional additives such as a chain extender, a cross-linking agent, a toughening agent and the like, the polybasic acid compound in the polyhydroxyalkanoate composition can reduce the thermal degradation effect in the thermal processing process, improve the molecular weight, improve the toughness of a formed body, improve the notch impact strength of an injection-molded body and improve the right-angle tear strength and the elongation at break of a film formed body. And compared with organic peroxide with the same crosslinking effect, the polybasic acid compound is more stable, so that the potential safety hazard caused by high activity such as the use of organic peroxide is effectively avoided in the production process, the difficulty of quantitative control of reaction is reduced, the processing operation is safer and simpler, and the processing efficiency of the polyhydroxyalkanoate resin is effectively improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The present invention is described in more detail by the following examples, which are not intended to limit the present invention. All the raw materials used in the following examples and comparative examples were commercially available except for the specific ones.

The method comprises the following steps:

poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP330, beijing blue-crystal Microbiol technologies, inc., 3HB (3-hydroxybutyrate unit) content of 94%, weight average molecular weight is not less than 50 ten thousand.

Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), product number: BP350, beijing blue-crystal Microbiol technologies, inc., 3HB (3-hydroxybutyrate unit) content 89%, weight average molecular weight more than or equal to 50 ten thousand.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with a weight average molecular weight of greater than or equal to 50 ten thousand, beijing Lanjing Microbiol technologies, inc.

Poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P34 HB), weight average molecular weight is more than or equal to 50 ten thousand, beijing blue crystal Microbiol. Co., ltd.

Poly (3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHBO) with a weight average molecular weight of 50 ten thousand or more, beijing blue Crystal Microbiol. Co., ltd.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate (P3 HB3HV3 HH), weight average molecular weight ≥ 50 ten thousand, beijing Lanjing Microbiol technologies, inc.

The adopted equipment comprises the following steps:

mixing equipment: blending at room temperature in a high-speed blender.

And (3) granulating equipment: the common extrusion granulation equipment in the field such as a parallel co-rotating twin-screw extruder, a parallel counter-rotating twin-screw extruder, a conical twin-screw extruder and a single-screw extruder with different length-diameter ratios can be used; placing the composition in a discharge hopper or a weightless scale of a twin-screw extruder; the temperature of the extrusion granulation equipment is set in the range of 50-180 ℃ (the first temperature), the rotating speed of the main machine is 50-500 r/min, and the feeding amount or the productivity is adjusted according to the actual production state; subsequently, granulation can be carried out in the granulation modes of air cooling bracing granulation, water bath bracing granulation, grinding surface hot cutting, water ring cutting, underwater granulation and the like, and the water bath condition of 40-65 ℃ (the second temperature) is kept in the production and processing process; the prepared particles are dried by using an air-blast drying oven, the influence of moisture on the particle performance is eliminated, and the particles are completely crystallized.

Film making equipment: adopting common film or pipe making equipment in the field such as a single-layer or multi-layer film blowing machine, and setting the temperature of a screw and a die head to be 50-180 ℃ (a first temperature); the prepared film is subjected to on-line crystallization under the condition of 40-65 ℃ by using a drying tunnel before being rolled.

Evaluation of the properties of the molded polyhydroxyalkanoate products:

weight average molecular weight:

the measurement was performed by polystyrene conversion using a gel permeation chromatograph (HPLCGPCsystem, manufactured by shimadzu corporation) using a chloroform solution. As the column in the gel permeation chromatograph, a column suitable for measuring a weight average molecular weight may be used.

Melt flow rate:

the melt flow rate was measured according to ISO 1133-1; the melt flow rate is given in g/10min.

Tensile strength and elongation at break:

according to ISO 527-2; tensile strength in MPa and elongation at break in%.

Notched impact strength:

according to ISO 179-1; the unit is kJ/m ² 。

Evaluation method of properties of polyhydroxyalkanoate film molded body:

machine direction tensile strength and machine direction elongation at break of the film:

the film shaped bodies were tested according to ISO527-2-2012 for tensile strength and elongation at break in the machine direction at a test speed of 500 mm/min; the film had a machine direction tensile strength in MPa and a machine direction elongation at break in%.

Longitudinal right angle tear strength of film:

the test of the film forming body is carried out according to QB/T1130-1991, and the longitudinal right-angle tear strength of the film forming body is measured under the condition that the test speed is 200 mm/min; the film has a longitudinal right angle tear strength in kN/m.

Molded article of polyhydroxyalkanoate particles

Preparing a particle forming body, and extruding and granulating by adopting a double screw; the polyhydroxyalkanoate compositions used in the tables are examples 1-22 and comparative examples 1-4, respectively.

The method for producing molded articles of polyhydroxyalkanoate particles comprises the following steps:

step 1, mixing materials: putting polyhydroxyalkanoate powder and a polybasic acid compound into a high-speed mixer, and mixing at room temperature at the mixing speed of 200r/min for 5min; after mixing, the mixed material was placed in the discharge hopper of a twin-screw extruder.

Step 2, extrusion: the conditions of the extrusion granulation equipment are set, and the extrusion is carried out under the condition that the melt temperature is about 165 ℃.

Step 3, granulation and cooling: granulating by adopting a water bath bracing and granulating mode, wherein the water bath heating temperature is 50 ℃.

The performance parameters of each molded article of polyhydroxyalkanoate particles are shown in tables 1 to 2.

TABLE 1

TABLE 2

Referring to tables 1 and 2, it can be seen from the experimental data of comparative example 1 and examples 1 to 13 that, compared with the polyhydroxyalkanoate composition without the addition of the polybasic acid, the weight average molecular weight of the molded article can be significantly increased, the reduction of the melt flow rate is significant, and meanwhile, the tensile strength, the elongation at break and the notch impact strength of the molded article can be significantly increased, which is beneficial to the improvement of the mechanical properties of the molded article and the expansion of the application range of the particle molded article.

Further, as can be seen from the experimental results of examples 4 and 6 and comparative examples 1 to 2, although the weight average molecular weight of comparative example 2 using the chain extender ADR-4468 is slightly larger than that of comparative example 1 without addition, the molded article prepared by combining the polyhydroxyalkanoate and the polyacid compound as in examples 4 and 6 has a higher weight average molecular weight than the conventional chain extender, which also confirms that the polyacid and the chain extender can increase the weight average molecular weight of the polyhydroxyalkanoate resin, but the melt flow rate of comparative example 2 with addition of the chain extender ADR-4468 is not significantly reduced and the elongation at break is not significantly increased, and it can be seen that the known chain extender does not achieve the effect of the polyacid in the present application.

The present study found that the effect of the polybasic acids with known chain extenders is different, primarily due to the different reactivity of the two classes of materials with polyhydroxyalkanoates. The known chain extender is a substance with multiple active groups, and the chain length is extended through the reaction of the multiple active groups and other resin materials (the multiple active groups can directly react with low-molecular-mass oligomers to form bridges between two polymer chains, thereby obviously increasing the molecular mass); however, through research on a plurality of known chain extenders, it is found that for polyhydroxyalkanoates, since the molecular weight of polyhydroxyalkanoates is larger than that of other polyester materials, and meanwhile, the known chain extenders (such as ADR) are polymers with a certain molecular weight, during the thermoplastic processing, the thermal motions of the two are weak, and it is difficult for active groups of the chain extender to reach between two polyhydroxyalkanoate molecular chains to form chain extension.

Further research finds that the polybasic acid compound has smaller molecular weight and stronger molecular thermal motion, and is easier to react between two polyhydroxyalkanoate molecular chains to form chain extension, so that the molecular weight of the formed body can be improved, the problem of reduction of the polyhydroxyalkanoate molecular weight caused by large thermal degradation degree in the processing process is counteracted, and the prepared formed body has lower melt flow rate.

In addition, the present inventors have found that the addition of the polybasic acid type compound allows the production of a molded article having higher tensile strength, elongation at break and notched impact strength, which is manifested by increased toughness of the molded article, and the efficacy of such toughening is different from that of a conventional plasticizer, that is, the polybasic acid type compound has the function of increasing the weight average molecular weight of the polyhydroxyalkanoate resin while also greatly increasing the toughness of the resin. The known common toughening agent can only increase the toughness of the resin, which also illustrates that the invention adopts the polybasic acid compound to reduce the thermal degradation of the polyhydroxyalkanoate resin and play an effective toughening role, so that the polyhydroxyalkanoate forming body has the advantages of good processing stability and good mechanical property.

From the experimental results of examples 5, 7 to 9, 11 to 12 and comparative example 3, it can be seen that the polyhydroxyalkanoate molded bodies prepared by using the combination of the polybasic acid type compounds can effectively increase the weight average molecular weight and decrease the melt flow rate, and also have higher tensile strength, elongation at break and notched impact strength, compared to the monobasic acid type compounds. This is probably because the polybasic acid compound has more carboxyl group ends than the monobasic acid, which is more beneficial to obviously improving the function of weight average molecular weight, and the surface tests prove that the polybasic acid compound has the reactivity linked chain extension of the polycarboxyl group on the polyhydroxyalkanoate in the mechanism.

Further, in order to further investigate whether the inorganic acid also has a similar effect, as in comparative example 4 using boric acid as a comparison, it can be seen from the experimental results of examples of the present invention that although the inorganic boric acid is combined with polyhydroxyalkanoate to prepare a molded body, the weight average molecular weight of the molded body can be increased, the decrease of the melt flow rate of the molded body is insignificant, and the tensile strength, elongation at break and notched impact strength are low, it is apparent that the inorganic acid does not have a similar effect as the organic polybasic acid. In addition, boric acid is not commonly used for producing a shaped article having a touch-ability in view of its harmful effects on the human body.

It was found that when the amount of the polybasic acid type compound added to the polyhydroxyalkanoate composition is in the range of 0.01% to 20%, the weight average molecular weight of the molded article produced is higher than that of a molded article produced without the addition of the polybasic acid type compound. When the addition amount is too low or too high, the effect is not remarkable. After further research, the addition amount of the polybasic acid compound can be controlled to be 0.05-5%. Further, the addition of adipic acid in an amount of 2.5% based on the polyhydroxyalkanoate as in example 13 started to be smaller than in examples 1 to 3, i.e., the weight average molecular weight of the molded article was not further increased, resulting in an increase in melt flow rate, which may affect the processability of the molded article, probably because the increase in the addition amount rather reduces the effect of counteracting thermal degradation, but the effect of counteracting thermal degradation is more remarkable than that of comparative example 1 and other types of polybasic acid compounds which were not added. Therefore, the amount of the polybasic acid compound to be added is preferably controlled to 0.05% to 2.5%.

Further, from the experimental results of example 9 and examples 5, 7, 8, 11, and 12, it can be seen that, compared with the case of using an organic tribasic acid as the polybasic acid compound in combination with polyhydroxyalkanoate to prepare the molded body, the use of an organic dibasic acid as the polybasic acid compound can more effectively increase the weight average molecular weight of the molded body, and more effectively improve the mechanical properties of the molded body, such as elongation at break, notched impact strength, and the like, and further more effectively improve the overall properties of the molded body.

From the experimental results of example 7 and examples 5, 8, 11 and 12, it can be seen that, compared with the molded articles prepared by using an unsaturated dibasic acid as the polybasic acid compound and an organic saturated dibasic acid as the polybasic acid compound, the molded article in example 7 has a larger weight average molecular weight, but a larger melt flow rate and a lower elongation at break, and thus the saturated dibasic acid compound can more effectively reduce the melt flow rate of the molded article and effectively increase the elongation at break of the molded article, and further more effectively improve the overall performance of the molded article.

Further studies have found that when an organic polybasic acid is used as the polybasic acid compound and a polyhydroxyalkanoate is used in combination to prepare a molded article, the problem of molecular weight reduction due to thermal degradation can be solved as a whole, but the effects of organic acids having different carbon chain lengths are slightly different, and as compared with glutaric acid used in example 5, the weight average molecular weight of example 8 is clearly lower than that of example 5, as in example 8. Similarly, in example 5, the weight average molecular weight is significantly lower than in examples 11 and 12 (dodecanedioic acid and hexadecanedioic acid were used, respectively) compared to examples 11 and 12.

TABLE 3

From the experimental data of table 3 it can further be stated that the organic diacids of the present invention are more stable as polyacid compounds during processing of the shaped bodies than other types of auxiliaries. The polyhydroxyalkanoate in the polyhydroxyalkanoate composition provided by the invention can be one or more polymers, and the polybasic acid compound can be one or more polybasic acid compounds. Molded articles comprising PHBH, PHBV, P34HB, PHBO, P3HB3HV3HH were prepared by adding one or a combination of succinic acid, adipic acid, glutaric acid, terephthalic acid, and DL-tartaric acid as the polybasic acid compound to polyhydroxyalkanoates of different monomers as in examples 14 to 22. Although the shaped bodies prepared in examples 14 to 22 have slightly different weight-average molecular weights, it can be seen overall that the composition A according to the invention acts to counteract thermal degradation for different polyhydroxyalkanoates or combinations thereof.

Preparation of polyhydroxyalkanoate film

Further, polyhydroxyalkanoate film is prepared by selecting the molded article of polyhydroxyalkanoate particles prepared in example 1, example 2, example 3, example 6, example 8, example 16, example 17, example 18, comparative example 1, comparative example 2, comparative example 3, and comparative example 4 described above and placing the molded article in a single layer or multilayer film blowing machine, and setting the temperature of a screw and a die to be 50 ℃ to 160 ℃ (first temperature); the prepared film is subjected to on-line crystallization under the condition of 55 ℃ by using a drying tunnel before being rolled. Before the film is prepared, the prepared polyhydroxyalkanoate particle forming body is dried for more than 4 hours at the temperature of 60 ℃ by using an air-blast drying oven, the influence of moisture on the particle performance is eliminated, and the particles are completely crystallized. Specific embodiments are shown in table 4 below.

TABLE 4

It should be noted here that the film-formed article may be directly prepared from a mixed raw powder of the polyhydroxyalkanoate composition of the present invention, and is not limited to the above-described granulated pellet as a raw material for preparing a film. In practical applications, the raw material used for preparing the film forming body may be a formed body having the same or similar composition as the raw material, such as waste scraps produced by processing, or a mixture of the waste scraps and the raw powder.

The experimental results in table 4 show that, compared with the commonly used chain extender, inorganic acid and organic monoacid, the organic diacid is used as the polybasic acid compound and is combined with the polyhydroxyalkanoate to prepare the formed film, the formed film can be continuously and stably processed into a film, the longitudinal tensile strength and the longitudinal elongation at break of the film are good, the right-angle tearing strength is high, and the film has a wide application scene.

Finally, it should be noted that: the above is only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing, those of ordinary skill in the art will understand that: the technical solutions mentioned above can still be modified, or some technical features can be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims (10)

1. A polybasic acid-containing polyhydroxyalkanoate composition, comprising a polyhydroxyalkanoate and a polybasic acid compound;

the polybasic acid compound is an organic polybasic acid compound represented by a general formula R' (COOH) n;

wherein R' is represented by: a hydrocarbon group containing 2 to 30 carbon atoms, or a group composed of one or more of an aryl group, an epoxy group, an ether bond, a hydroxyl group, and a hydrocarbon group containing 2 to 30 carbon atoms;

n is an integer of 2 or more.

2. The polyhydroxyalkanoate composition of claim 1, wherein the polybasic acid compound is added in an amount of 0.01% to 20% by mass of the polyhydroxyalkanoate.

3. The polyhydroxyalkanoate composition of claim 2, wherein the polybasic acid compound is added in an amount of 0.05% to 5% by mass of the polyhydroxyalkanoate.

4. A polyhydroxyalkanoate composition according to any one of claims 1-3, wherein the polyacid compound is an organic diacid and/or an organic triacid of the structure R' (COOH) n, where n is 2 or 3.

5. The polyhydroxyalkanoate composition of claim 4, wherein the polyacid compound is an organic saturated dibasic acid and/or an organic saturated tribasic acid.

6. The polyhydroxyalkanoate composition of claim 5, wherein the polyacid compound is selected from one or more of oxalic acid, malonic acid, succinic acid, tartaric acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, tricosanedioic acid, tetracosanedioic acid, pentacosanedioic acid, hexacosanedioic acid, heptacosanedioic acid, 1,3, 5-tricarboxypentane.

7. The polyhydroxyalkanoate composition of claim 4, wherein the polyacid compound is an organic diacid.

8. The polyhydroxyalkanoate composition of claim 7, wherein the polyacid compound is selected from one or more of succinic acid, tartaric acid, glutaric acid, adipic acid, dodecanedioic acid, hexadecanedioic acid.

9. A polyhydroxyalkanoate molded body, comprising the polyhydroxyalkanoate composition of any one of claims 1 to 8.

10. A process for the preparation of the polyhydroxyalkanoate shaped bodies of claim 9.