CN114276511A

CN114276511A - Branched block copolymer and preparation method thereof

Info

Publication number: CN114276511A
Application number: CN202210020264.8A
Authority: CN
Inventors: 裴承度; 陈志明; 梁伟; 马高琪; 王良波; 徐宁; 韩梦超; 林秀锦; 金洁
Original assignee: Zhejiang Hisun Biomaterials Co ltd
Current assignee: Zhejiang Hisun Biomaterials Co ltd
Priority date: 2022-01-10
Filing date: 2022-01-10
Publication date: 2022-04-05
Anticipated expiration: 2042-01-10
Also published as: CN114276511B

Abstract

The present invention relates to a branched block copolymer and a method for preparing the same, the branched block copolymer comprising: the polylactic acid polyether prepolymer, the branched block copolymer obtained by the reaction of the polycaprolactone prepolymer and diisocyanate, wherein the polylactic acid polyether prepolymer comprises a structure of the following formula (I):

wherein n and n' are integers independently selected from 5 to 500; a represents a polyether moiety; the polycaprolactone prepolymer comprises a structure shown in the following formula (II):

Description

Branched block copolymer and preparation method thereof

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a branched block copolymer and a preparation method thereof.

Background

Polylactic acid is a novel biodegradable material, has excellent biodegradability, compatibility and absorbability, can be processed like general thermoplastic plastics, such as extrusion, film blowing, tape casting molding, bottle blowing, injection molding, fiber forming and the like, and can be widely applied to various industrial, civil and medical special fields such as packaging, textile and the like. However, it has some disadvantages, such as a brittle material at normal temperature due to its high glass transition temperature, and poor impact resistance and thermal stability. Therefore, the polylactic acid is modified, the fluidity and the mechanical property of the polylactic acid are improved, and the application field of the polylactic acid can be greatly improved.

In the use process of polylactic acid, in order to make up for the defects of the performance of the polylactic acid, CN111675888A relates to a preparation method of a polylactic acid-based composite material with high tensile strength, high impact strength and high ductility, wherein the composite material is prepared by melt blending polylactic acid and phenoxy resin, and the phenoxy resin accounts for 1-20 wt% of the mass of the composite material; wherein the weight average molecular weight of the phenoxy resin is more than 2 ten thousand.

CN112694730A provides a preparation method for preparing high-performance high-fluidity polylactic acid based on hyperbranched polymer, which utilizes hyperbranched polymer as a flow aid, and blends hyperbranched polymer with a specific structure with polylactic acid material under a specific addition amount to obtain the polylactic acid composite material with high melt fluidity and complete biodegradability.

Disclosure of Invention

In one aspect, the present invention relates to a branched block copolymer comprising: a branched block copolymer obtained by the reaction of a polylactic acid polyether prepolymer, a polycaprolactone prepolymer and diisocyanate, wherein,

the polylactic acid polyether prepolymer comprises a structure shown in the following formula (I):

wherein the content of the first and second substances,

n, n' are integers each independently selected from 5 to 500;

a represents a polyether moiety;

the polycaprolactone prepolymer comprises a structure shown in the following formula (II):

wherein the content of the first and second substances,

p is an integer selected from 40 to 500,

l, L' are each independently selected from structures containing 2-10 hydroxyl groups.

In another aspect, the present invention also relates to a process for preparing the branched block copolymer of the present invention, comprising: step (1): lactide and polyether are reacted to prepare a polylactic acid polyether prepolymer; step (2): reacting epsilon-caprolactone with polyhydric alcohol, and carrying out ring-opening polymerization on the epsilon-caprolactone to prepare a polycaprolactone prepolymer; and (3): reacting and extruding the polylactic acid polyether prepolymer prepared in the step (1), the polycaprolactone prepolymer prepared in the step (2) and diisocyanate by an extruder to prepare a branched block copolymer; wherein the polyol is one or more selected from polyols containing 3 to 11 hydroxyl groups.

Detailed Description

General definitions and terms

All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety if not otherwise indicated.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the definitions provided herein will control.

All percentages, parts, ratios, etc., are by weight unless otherwise indicated.

When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a pair of upper and lower preferable values or specific values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. When numerical ranges are recited herein, unless otherwise stated, the stated ranges are meant to include the endpoints thereof, and all integers and fractions within the ranges. The scope of the invention is not limited to the specific values recited when defining a range. For example, "1-8" encompasses 1,2, 3, 4, 5, 6, 7, 8, as well as any subrange consisting of any two values therein, e.g., 2-6, 3-5.

The terms "about" and "approximately," when used in conjunction with a numerical variable, generally mean that the value of the variable and all values of the variable are within experimental error (e.g., within 95% confidence interval for the mean) or within ± 10% of the specified value, or more.

The terms "comprising," "including," "having," "containing," or "involving," and other variations thereof herein, are inclusive or open-ended and do not exclude additional unrecited elements or method steps. It will be understood by those skilled in the art that terms such as "including" and "comprising" encompass the meaning of "consisting of …. The expression "consisting of …" excludes any element, step or ingredient not specified. The expression "consisting essentially of …" means that the scope is limited to the specified elements, steps or components, plus optional elements, steps or components that do not materially affect the basic and novel characteristics of the claimed subject matter. It is to be understood that the expression "comprising" covers the expressions "consisting essentially of …" and "consisting of …".

The term "selected from …" means that one or more elements in the later listed groups are independently selected and may include a combination of two or more elements.

When values or range ends are described herein, it is to be understood that the disclosure includes the particular values or ends recited.

The term "one or more" or "at least one" as used herein refers to one, two, three, four, five, six, seven, eight, nine or more.

Unless otherwise indicated, the terms "combination thereof" and "mixture thereof" refer to a multi-component mixture of the elements described, such as two, three, four, and up to the maximum possible multi-component mixture.

Furthermore, no number of elements or components of the invention has been previously indicated and no limitation on the number of occurrences (or presence) of an element or component is intended. Thus, it should be read to include one or at least one and singular forms of a component or ingredient also include the plural unless the numerical value explicitly indicates the singular.

The terms "optionally" or "optionally" as used herein mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

When the lower and upper limits of a range of values are disclosed, any value falling within the range and any included range is specifically disclosed. In particular, each range of values (in the form "about a to b", or equivalently, "about a-b") disclosed herein is to be understood as meaning each number and range encompassed within the broader range.

For example, the expression "C_1-6"is to be understood to cover any subrange therein as well as each point value, e.g. C_2-5、C_3-4、C₁-₂、C_1-3、C_1-4、C_1-5Etc. and C₁、C₂、C₃、C₄、C₅、C₆And the like. For example, the expression "C_3-10"should also be done in a similar mannerIt is understood that any subranges and point values included therein, for example, may be encompassed. The expression "5-10, etc. should also be understood in a similar manner, e.g. any subrange and point values comprised therein may be covered, e.g. 5-6, 5-7, 5-8, 5-9, 5-10, 6-7, 6-8, 6-9, 6-10, 7-8 etc. as well as 5, 6, 7, 8, 9, 10 etc.

The term "hydrocarbon chain" as used herein may refer to a saturated or unsaturated chain consisting only of carbon and hydrogen. The unsaturated hydrocarbon chain contains at least one carbon-carbon double bond and/or carbon-carbon triple bond.

The term "ether chain" may refer herein to two or more hydrocarbon chains connected by an oxygen atom.

The term "alkyl", used herein alone or in combination with other groups, refers to a saturated straight or branched chain hydrocarbon group. The alkyl group may be C_1-6An alkyl group. As used herein, the term "C_1-6Alkyl "refers to a saturated straight or branched chain hydrocarbon group having 1 to 6 carbon atoms (e.g., 1,2, 3, 4, 5, or 6 carbon atoms). E.g. "C_1-6Alkyl "may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, or n-hexyl, and the like.

The term "alkoxy", used herein alone or in combination with other groups, refers to an alkyl group attached to the rest of the molecule through an oxygen atom. The alkoxy group may be C_1-6An alkoxy group.

The term "cycloalkyl", used herein alone or in combination with other groups, refers to a saturated hydrocarbon ring comprising a cyclic structure. The cycloalkyl group may be C_3-8A cycloalkyl group. Examples thereof include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like.

The term "heterocyclyl" broadly refers to aliphatic hydrocarbons comprising a cyclic structure, typically having from 3 to 12 ring atoms, containing at least 2 carbon atoms, and further containing from 1 to 3 heteroatoms independently selected from oxygen, sulfur and nitrogen. "heterocycle" also refers to a 5-to 7-membered heterocyclic ring fused to 5-and 6-membered aromatic carbocyclic rings containing one or more heteroatoms selected from nitrogen, oxygen, and sulfur, provided that the site of attachment is on the heterocyclic ring. Heterocycles may be saturated or contain one to more double bonds (i.e., partially unsaturated). The heterocyclic ring may be substituted with oxo (oxo). Either the carbon atom or the heteroatom of the heterocycle may be the attachment site, provided that a stable structure is formed. When a substituent is present on the heterocycle, the substituent may be attached to any heteroatom or carbon atom on the heterocycle, provided that a stable chemical structure is formed. The heterocyclic and heteroaryl definitions described herein do not overlap.

The term "aryl", used herein alone or in combination with other groups, refers to an all-carbon monocyclic or fused polycyclic (e.g., bicyclic) aromatic group having a conjugated pi-electron system. Aryl may be "C_6-10Aryl ". As used herein, the term "C_6-10Aryl "refers to an aromatic group containing 6 to 10 carbon atoms. Examples include, but are not limited to, phenyl and naphthyl.

The term "heteroaryl", used herein alone or in combination with other groups, refers to an aromatic group in which one or more (e.g., 1,2, or 3) ring atoms are heteroatoms selected from N, O and S, and the remaining ring atoms are C. Heteroaryl groups can be characterized by the number of ring atoms. Heteroaryl groups may be 5-10 membered heteroaryl groups in which one or more (e.g. 1,2 or 3) ring atoms are heteroatoms selected from N, O and S. For example, a 5-10 membered heteroaryl group may contain 5-10 ring atoms (e.g., 5, 6, 7, 8, 9, or 10) and particularly contains 5, 6, 9, 10 ring atoms. And in each case the heteroaryl group may optionally be further benzo-fused. For example, examples of heteroaryl groups are thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, pyrazinyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl and the like, and benzo derivatives thereof; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolinyl, isoquinolinyl, benzofuranyl, benzothienyl, indolyl, isoindolyl, and the like, and benzo derivatives thereof.

The terms "substituted" and "substituted" mean that one or more (e.g., one, two, three, or four) hydrogens on the designated atom is replaced with a selection from the indicated group, provided that the designated atom's normal valency in the current situation is not exceeded and that the substitution results in a stable compound. Combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

The term "halogen" refers to fluorine, chlorine, bromine, iodine.

If a substituent is described as "optionally … substituted," the substituent may be (1) unsubstituted or (2) substituted. If an atom or group is described as optionally substituted with one or more of a list of substituents, one or more hydrogens on the atom or group may be replaced with an independently selected, optional substituent. If a substituent is described as "independently selected from" or "each independently is," each substituent is selected independently of the other. Thus, each substituent may be the same as or different from another (other) substituent. For example, a certain substituent or substitution position or different substituents or substitution positions have R groups (such as but not limited to R) that may be designated by the same or different symbols³、R^a、R^b、R^cAnd/or R^x) In the selection of (3), R's are independently selected from each other, and may be the same or different. The same is true with regard to the choice of values such as m, n.

Herein, when a wavy line is shown on a chemical bond in a structural fragment, it means that the bond is linked to another structure. For example:

indicating that the benzene ring is linked to another structure through a bond on which a wavy line is shown.

Unless indicated, as used herein, the point of attachment of a substituent may be from any suitable position of the substituent.

When a bond of a substituent is shown through a bond connecting two atoms in a ring, then such substituent may be bonded to any ring atom in the substitutable ring.

The term "aromatic hydrocarbon", as used herein, alone or in combination with other terms, refers to an all-carbon monocyclic or fused polycyclic (e.g., bicyclic) aromatic hydrocarbon having 6 to 10 carbon atoms, examples of which include benzene and naphthalene, particularly benzene.

The term "repeating unit" refers to a combination of atoms linked in a certain manner on a polymer chain, which is an essential unit constituting a polymer.

As used herein, the term "room temperature" (RT) refers to about 20 to 35 ℃, preferably about 25 ℃.

In one aspect, the present invention relates to a branched block copolymer comprising: the branched block copolymer is obtained by the reaction of polylactic acid polyether prepolymer, polycaprolactone prepolymer and diisocyanate.

Polylactic acid polyether prepolymer

wherein n and n 'represent the number of repeating units, and n' are integers independently selected from 5 to 500, such as 5, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.; a represents a polyether moiety.

The polylactic acid polyether prepolymer can be prepared by the reaction of lactide and polyether, and comprises a polylactic acid part and a polyether part. The polylactic acid polyether prepolymer has hydroxyl functional groups at both ends, and the hydroxyl end groups can react with diisocyanate in a subsequent step to form a final branched block copolymer.

The polylactic acid part can enable the final product branched block copolymer to have excellent biodegradability, compatibility and absorbability, and is easy to process.

In one embodiment of the present invention, n and n' in formula (I) are integers independently selected from 5 to 500. The overlong chain length of the polylactic acid part can cause the activity of reaction groups (namely hydroxyl) at two ends of the polylactic acid polyether prepolymer to be reduced, and the subsequent reaction with diisocyanate is not facilitated; the chain length is too short, the molecular weight of the final branched block copolymer is low, and various mechanical properties are poor.

Since polylactic acid has a generally high glass transition temperature, it is a brittle material at normal temperature, and its impact resistance and thermal stability are generally poor. The polyether part is introduced and used as a soft segment, so that the branched block copolymer of the final product can be endowed with a lower glass transition temperature, and meanwhile, the toughness and heat resistance of the branched block copolymer are improved, so that the product has the characteristics of high elongation, slow crystallization and the like.

The polyether has an ether bond in its main chain and hydroxyl functional groups at both ends. The polyether participates in the ring-opening polymerization of lactide through hydroxyl groups of the polyether, so that a polylactic acid polyether prepolymer is formed, wherein two ends of the polyether part are connected with polylactic acid parts. In one embodiment, the structure of the polyether moiety consists of a single repeating unit. Can be prepared by selecting corresponding polyether. In one embodiment, the structure of the polyether moiety is comprised of more than two repeating units. Can be prepared by selecting the corresponding block polyether.

In one embodiment of the present invention, the polyether moiety represented by a comprises a structure selected from the group consisting of:

wherein X is selected from a linear or branched hydrocarbon chain of 2 to 10 carbon atoms, said hydrocarbon chain being optionally substituted, each independently, with one or more substituents selected from alkyl, cycloalkyl, alkoxy, cyano, aryl and heteroaryl; m is an integer selected from 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, and the like.

It will be understood that when the polyether moiety includes a combination of two or more structures, the structures are linked by ether linkages, one possible structure being as follows:

wherein X, X' are each independently selected from a straight or branched hydrocarbon chain of 2 to 10 carbon atoms, said hydrocarbon chain optionally each independently substituted with one or more substituents selected from alkyl, cycloalkyl, alkoxy, cyano, aryl and heteroaryl; m, m' are each independently selected integers from 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, and the like.

In a particular embodiment, the polyether moiety comprises a structure selected from the group consisting of:

wherein m is₁、m₂、m₃Each independently selected from integers of 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, and the like.

It is to be understood that when the polyether moiety is composed of two or more of the formula (III-1), the formula (III-2) and the formula (III-3), the structures are linked to each other through an ether bond.

For example, when the polyether moiety is composed of the formula (III-1) or the formula (III-2), one of the possible structures is as follows:

wherein m is₁、m₂As defined above.

The chain length of the polyether part is too long, the hydroxyl groups at two ends of the polyether part have low reaction activity, and the polyether part is not beneficial to reacting with lactide to form a polylactic acid polyether prepolymer; the chain length is too short, the prepared polylactic acid polyether prepolymer has low molecular weight, and the finally prepared branched block copolymer has low molecular weight and poor mechanical properties. In one embodiment, m₁、m₂、m₃Each independently selected from integers of 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, and the like.

In one embodiment of the present invention, in formula (I), the weight ratio (i.e., the ratio of relative molecular weights) of the polyether moiety and the polylactic acid moiety is from 100:1 to 20, preferably from 100:1 to 15. The proper weight ratio is helpful for improving the properties of toughness, heat resistance, fluidity and the like of the final product.

The molecular weight of the polylactic acid polyether prepolymer affects the reactivity with diisocyanate in the subsequent steps, and the properties of the final product (e.g., molecular weight, melting point, melt index, relative viscosity, tensile strength, notched impact strength, elongation at break, etc.). In one embodiment, the number average molecular weight of the polylactic acid polyether prepolymer is 5000-. The molecular weight of the polylactic acid polyether prepolymer is too high, and the hydroxyl groups at two ends of the polylactic acid polyether prepolymer have low reaction activity and are not beneficial to subsequent reaction with diisocyanate; the molecular weight is too low, the molecular weight of the prepared branched block copolymer is low, and various mechanical properties are poor.

Polycaprolactone prepolymer

The polycaprolactone prepolymer comprises a structure of the following formula (II):

wherein p represents the number of repeating units, and is an integer selected from 40 to 500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.; l, L' are each independently selected from structures containing 2-10 hydroxyl groups.

The epsilon-caprolactone is subjected to ring-opening polymerization through the reaction of the epsilon-caprolactone and the polyalcohol to prepare the polycaprolactone prepolymer. The two ends of the polycaprolactone prepolymer are corresponding structures (namely L, L 'in formula (II)) introduced by polyol, and a plurality of hydroxyl groups contained in L, L' can serve as reaction sites for branching in subsequent reactions, so that a final product, namely the branched block copolymer, is prepared.

The poly-epsilon-caprolactone part in the polycaprolactone prepolymer is formed through the ring-opening polymerization of epsilon-caprolactone. The poly-epsilon-caprolactone part is introduced, so that the fluidity and the mechanical property of the branched block copolymer of the final product can be further improved, the toughness and the heat resistance of the final product are enhanced, and the product has the characteristics of high fluidity, high elongation, high tensile strength and the like.

The chain length of the poly-epsilon-caprolactone part in the polycaprolactone prepolymer influences the subsequent polymerization. In one embodiment of the invention, p in formula (I) is an integer selected from 40 to 500. The chain length of the poly epsilon-caprolactone part is too long, the activity of the hydroxyl at the two ends of the polycaprolactone prepolymer is reduced, and the subsequent polymerization is not facilitated; the chain length is too short, the molecular weight of the finally prepared branched block copolymer is low, and various mechanical properties are poor.

The two ends of the polycaprolactone prepolymer (i.e. L, L' in formula (II)) are corresponding structures introduced by polyol. L, L' in the polycaprolactone prepolymer respectively and independently comprise at least two hydroxyl groups which are used as branching sites in subsequent reactions, so that the branched block copolymer of the final product with a branched structure is formed. L, L', the final branched block copolymer has too high a flowability, which affects its mechanical properties and its processability. In one embodiment, L, L' in formula (II) are each independently selected from structures comprising 2-10 hydroxyl groups, for example each independently selected from structures comprising 2, 3, 4, 5, 6, 7, 8, 9, 10 hydroxyl groups.

In one embodiment, L, L' in the polycaprolactone prepolymer are each independently selected from the group consisting of: c_3-20A linear or branched hydrocarbon chain of (C)_3-20The hydrocarbon chain and the ether chain are respectively and independently substituted by 2 to 10 hydroxyl groups; the hydrocarbon chain and the ether chain are respectively and independently optionally substituted by one or more R^xSubstituted with the substituent(s); the R is^xSelected from: c_3-20Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, cyano.

In one embodiment, L, L' in the polycaprolactone prepolymer are each independently selected from the following structures (IV-1) to (IV-4):

wherein, the C atoms in the formulas (IV-1) to (IV-4) are respectively and independently selected from one or more R^xSubstituted with the substituent(s); the R is^xSelected from: c_3-20Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, cyano.

In one embodiment, L, L' is a different structure in the polycaprolactone prepolymer.

In one embodiment, L, L' in the polycaprolactone prepolymer is the same structure.

In a specific embodiment, L, L' in the polycaprolactone prepolymer is of the structure shown in formula (IV-1). The polycaprolactone prepolymer can be prepared by taking pentaerythritol as a polyol to participate in the reaction.

In a specific embodiment, L, L' in the polycaprolactone prepolymer is of the structure shown in formula (IV-2). The polycaprolactone prepolymer can be prepared by selecting dipentaerythritol as polyol to participate in the reaction.

In a specific embodiment, L, L' in the polycaprolactone prepolymer are respectively and independently selected from structures shown in formulas (IV-3) and (IV-4). The polycaprolactone prepolymer can be prepared by taking tripentaerythritol as a polyol to participate in the reaction.

The molecular weight of the polycaprolactone prepolymer influences the reactivity with diisocyanate in the subsequent steps, the molecular weight of the final product and various mechanical properties. The molecular weight of the polycaprolactone prepolymer is too high, and the hydroxyl reaction activity in the polycaprolactone prepolymer is low, so that the subsequent reaction with diisocyanate is not facilitated; the molecular weight is too low, the molecular weight of the finally prepared branched block copolymer is low, and various mechanical properties are poor. In one embodiment, the number average molecular weight of the polycaprolactone prepolymer is 5000-.

Diisocyanate

In this context, diisocyanate refers to a compound containing two isocyanate groups. The two isocyanate groups contained in the structure react with the hydroxyl groups of the polylactic acid polyether prepolymer and the polycaprolactone prepolymer, and the final product, namely the branched block copolymer, is obtained through copolymerization.

The diisocyanate to be used is not particularly limited, and includes two isocyanate groups in its structure so that the copolymerization reaction proceeds smoothly. Too high a number of isocyanate groups (for example more than 3) results in a copolymer which is too crosslinked to facilitate subsequent processing.

The aromatic diisocyanates herein contain two isocyanate groups, at least one of which is located on an aromatic ring (e.g., benzene ring, naphthalene ring, etc.). The aromatic diisocyanate has higher molecular reaction activity, is beneficial to the subsequent reaction, and is beneficial to increasing the mechanical properties such as the strength of the product due to the existence of a rigid aromatic ring structure. In a preferred embodiment, both isocyanate groups of the aromatic diisocyanate are located on the aromatic ring. The isocyanate group acts as an electron withdrawing group and can increase the reactivity of another isocyanate group located on the same aromatic ring.

In one embodiment, the diisocyanate is selected from the group consisting of: 1, 5-naphthalene diisocyanate, toluene-2, 4-diisocyanate, diphenylmethane diisocyanate, and combinations thereof.

Branched block copolymers

The branched block copolymer comprises: a branched block copolymer obtained by the reaction of a polylactic acid polyether prepolymer, a polycaprolactone prepolymer and diisocyanate.

The diisocyanate reacts with the hydroxyl groups of the polylactic acid polyether prepolymer and the polycaprolactone prepolymer, the polyhydroxy in the polycaprolactone prepolymer is used as a branching site, and the polylactic acid polyether prepolymer and the polycaprolactone prepolymer are copolymerized to finally obtain a branched block copolymer.

The branched block copolymer is a terpolymer of polylactic acid-polyether-polycaprolactone, has high molecular weight, good melt flowability and heat resistance due to a branched chain structure, can be processed and molded at a low temperature, and avoids thermal degradation. Meanwhile, the heat resistance is better because the density of the physical crosslinking area is high. The introduction of the polyether and polycaprolactone block provides great toughness, and the defect of brittleness of polylactic acid is overcome

In one embodiment, hydroxyl groups contained in the structures of the polylactic acid polyether prepolymer and the polycaprolactone prepolymer are reacted with diisocyanate, so that copolymerization is carried out to obtain the branched block copolymer. The branched block copolymer has excellent properties such as good fluidity, toughness and the like, and is beneficial to subsequent processing and use.

The molecular weight of the branched block polymer influences the mechanical properties of the branched block polymer, and too low molecular weight can result in overlarge polymer flowability and poor mechanical properties. In one embodiment, the branched block polymer of the present invention has a number average molecular weight of 100000 or more, such as about 100000-1000000, such as about 135000, about 126000, about 138000, about 119000, about 128000, about 136000, about 127000, about 137000.

Preparation method

In another aspect, the present invention also relates to a process for the preparation of a branched block copolymer comprising at least the steps of:

step (1): lactide and polyether are reacted to prepare the polylactic acid polyether prepolymer;

step (2): reacting epsilon-caprolactone with polyalcohol, and carrying out ring-opening polymerization on the epsilon-caprolactone to prepare the polycaprolactone prepolymer;

and (3): and (2) reacting and extruding the polylactic acid polyether prepolymer prepared in the step (1), the polycaprolactone prepolymer prepared in the step (2) and the diisocyanate through an extruder to prepare the branched block copolymer.

Wherein, the reaction sequence of the step (1) and the step (2) can be adjusted arbitrarily.

Step (1): and (3) reacting lactide with polyether to obtain the polylactic acid polyether prepolymer.

The polylactic acid polyether prepolymer comprises a polylactic acid part and a polyether part.

The polylactic acid moiety is obtained by ring-opening polymerization of lactide, and the lactide monomer configuration determines the configuration of the polylactic acid moiety. The lactide monomer that is finally inserted into the active end of the growing chain determines the configuration of the next lactide monomer inserted into the end of the polymer chain. The poly-L-lactic acid part can be obtained by ring-opening polymerization by using L-lactide as a raw material. The poly-D-lactic acid part can be obtained by ring-opening polymerization by using D-lactide as a raw material. The poly- (D, L) -lactic acid part can be obtained by ring-opening polymerization by using (D, L) -lactide as a raw material. The structural formulas of the L-lactide, the L-lactide and the (D, L) -lactide are respectively as follows.

The lactide used in the present invention is selected from the group consisting of L-lactide, D-lactide, (D, L) -lactide and combinations thereof, preferably L-lactide or D-lactide.

According to the selection of different polyethers, polylactic acid polyether prepolymers with different polyether parts can be obtained, so that the performance of the final product, namely the branched block polymer, is improved. The suitable polyether has good reactivity, and can enhance the toughness of the branched block polymer of the final product, so that the branched block polymer has better mechanical properties. The polyether used in the present invention is not particularly limited. In one embodiment, the polyether used is a polyether consisting of a single repeating unit. In one embodiment, the polyether used is a block polyether.

In one embodiment, the polyether used in step (1) is polyethylene glycol. In another embodiment, the polyether used in step (1) is polypropylene glycol. In yet another embodiment, the polyether used in step (1) is polytetrahydrofuran.

The molecular weight of the polyether has an influence on the reactivity of the polyether and the molecular weight of the prepolymer of the polylactic acid polyether. The molecular weight of the polyether is too high, and the reactivity of the hydroxyl groups at both ends thereof is lowered, so that in the reaction of step (1), by-products are increased and partial blending occurs (for example, by-products in which a polylactic acid moiety is bonded to only one end of a polyether moiety are generated); the low molecular weight is not favorable for improving the toughness of the polyether part, the low molecular weight of the prepared polylactic acid polyether prepolymer is not favorable for the subsequent reaction, and the obtained final product has poor formability and cannot be used in practical application. In one embodiment of the present invention, the polyether used in step (1) has a number average molecular weight of 1000-.

In the step (1), the ratio of lactide to polyether affects the acquisition of the target polylactic acid polyether prepolymer. When the ratio of lactide to polyether is too low, the formation of by-products is increased, thereby making it impossible to obtain the final product or reducing the yield of the final product. The obtained polylactic acid polyether prepolymer has too high molecular weight and too high viscosity, which is not beneficial to the subsequent reaction. When the ratio of lactide to polyether is too high, the molecular weight of the prepared polylactic acid polyether prepolymer is too low, and the content of small molecular components in the polylactic acid polyether prepolymer is higher, so that the performance of the final product branched block copolymer is influenced. In one embodiment, in step (1), the ratio of lactide to polyether is about 100:1 to 20, preferably about 100:1 to 15, for example about 100:10, about 100:15, about 100:5 by weight.

In one embodiment, a catalyst is used to catalyze the ring-opening polymerization of lactide in step (1) of preparing a polylactic acid polyether prepolymer. The addition of the catalyst can accelerate the rate of the ring-opening polymerization reaction, wherein the proper catalyst can effectively accelerate the rate of the reaction, the reaction is not influenced by the chemical properties of the catalyst, such as acidity, alkalinity, oxidizability, reducibility and the like, the proper catalyst can avoid the occurrence of side reactions and improve the concentration of the product.

In one embodiment, the catalyst used is selected from the group consisting of tin-based catalysts, zinc-based catalysts, and combinations thereof. The tin-based catalyst refers to a compound containing elemental tin, which may be an organotin compound or an inorganic tin compound. The zinc-based catalyst refers to a compound containing elemental zinc, which may be an organozinc compound or an inorganic zinc compound.

In one embodiment, the catalyst added in step (1) is selected from the group consisting of stannous octoate, zinc oxide, zinc chloride, stannous chloride, and combinations thereof.

The catalyst content affects the efficiency of the polymerization reaction to some extent and on the other hand the cost. In one embodiment, the ratio of lactide to catalyst in step (1) is from about 100:0.001 to 0.5, for example about 100:0.024, about 100:0.04, about 100:0.06, by weight.

Lactide and polyether are heated to be completely melted, and then other raw materials are added, so that the reaction system is more uniform, and the reaction yield is higher. In one embodiment, in step (1), the lactide and the polyether are heated to be completely molten, and then a catalyst is added to keep heating reaction for a certain time, so as to obtain the polylactic acid polyether prepolymer.

In a specific embodiment, the reaction temperature in step (1) is about 150 ℃ to about 210 ℃, e.g., about 160 ℃, about 180 ℃, about 190 ℃, about 150 ℃. Too high reaction temperature increases energy consumption in the reaction process, causes decomposition of reactants, and reduces yield of the target product; excessively low reaction temperature is disadvantageous in that the reaction occurs, the reaction rate is reduced, and the yield of the objective product is reduced.

The reaction time in step (1) is about 3 to 8 hours, for example, about 5 hours, about 4 hours, about 3 hours. Too short reaction time can cause incomplete reaction, the molecular weight of the product is too low, the yield is reduced, and the subsequent reaction is not facilitated; too long a reaction time increases energy consumption during the reaction and is liable to cause thermal degradation.

Under the environment of inert gas, the method is favorable for reducing side reaction and maintaining the activity of the catalyst. In one embodiment, step (1) is carried out under an inert gas atmosphere. In a particular embodiment, step (1) is carried out under a nitrogen atmosphere.

Step (2): and (2) reacting epsilon-caprolactone with polyol, and carrying out ring-opening polymerization on the epsilon-caprolactone to prepare the polycaprolactone prepolymer.

The epsilon-caprolactone is subjected to ring-opening polymerization through the reaction of the epsilon-caprolactone and the polyalcohol to prepare the polycaprolactone prepolymer. The polycaprolactone prepolymer comprises a poly-epsilon-caprolactone part and a corresponding structure introduced from polyol at two ends.

The polycaprolactone prepolymer prepared by selecting proper polyol has good reaction activity and proper branching sites, so that the final product branched block polymer has excellent performance. The polyol selected for use in the present invention is not particularly limited, and contains at least 3 hydroxyl groups. To serve as sites for branching in subsequent reactions. Too high a number of hydroxyl groups contained in the polyol leads to too high a flowability of the polymer, which adversely affects both its mechanical properties and its processability. In one embodiment, the polyol of the present invention comprises 3 to 11 hydroxyl groups, for example 3, 4, 5, 6, 7, 8, 9, 10, 11 hydroxyl groups.

In one embodiment, the polyol used in step (2) is selected from the following compounds: c_3-20A linear or branched hydrocarbon chain of (C)_3-20And the hydrocarbon chain, the ether chain each independently being substituted with 2 to 10 hydroxyl groups; wherein the hydrocarbon chain and the ether chain are respectively and independently optionally substituted by one or more R^xSubstituted with the substituent(s); r^xSelected from: c_3-20Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, cyano.

In one embodiment, the polyol used in step (2) is selected from: pentaerythritol, dipentaerythritol, tripentaerythritol, glycerol, trimethylolethane, trimethylolpropane, xylitol, 1,2, 5-pentanetriol, and combinations thereof.

In one embodiment, the polyol used in step (2) is pentaerythritol. In another embodiment, the polyol used in step (1) is dipentaerythritol. In yet another embodiment, the polyol used in step (2) is tripentaerythritol.

In one embodiment, two or more polyols are selected for step (2).

In one embodiment, a single polyol is selected for step (2).

In the step (1), the ratio of epsilon-caprolactone to polyalcohol influences the obtaining of the target polycaprolactone prepolymer. When the ratio of epsilon-caprolactone to the polyol is too low, the formation of by-products is increased, so that the final product cannot be obtained or the yield of the final product is lowered. The molecular weight and viscosity of the obtained polycaprolactone prepolymer are too high, which is not beneficial to the subsequent reaction. When the proportion of epsilon-caprolactone to the polyhydric alcohol is too high, the molecular weight of the prepared polycaprolactone prepolymer is too low, and the mechanical property and the processing property of a final product are influenced. In one embodiment, in step (2), the ratio of epsilon-caprolactone to polyol is from about 100:0.5 to 5, e.g., about 100:3, about 100:4, about 100:2, by weight.

In one embodiment, a catalyst is used in step (2) to catalyze the ring-opening polymerization of epsilon-caprolactone. The addition of the catalyst can accelerate the rate of the ring-opening polymerization reaction, wherein the proper catalyst can effectively accelerate the rate of the reaction, the reaction is not influenced by the chemical properties of the catalyst, such as acidity, alkalinity, oxidizability, reducibility and the like, the proper catalyst can avoid the occurrence of side reactions and improve the concentration of the product.

In one embodiment, the catalyst added in step (2) is selected from the group consisting of stannous octoate, zinc oxide, zinc chloride, stannous chloride, and combinations thereof.

The catalyst content affects the efficiency of the polymerization reaction to some extent and on the other hand the cost. In one embodiment, the ratio of epsilon-caprolactone to catalyst in step (2) is from about 100:0.001 to 0.5, for example about 100:0.024, about 100:0.04, about 100:0.06, by weight.

The epsilon-caprolactone and the polyhydric alcohol are heated to be completely molten, and then the rest raw materials are added, so that the reaction system is more uniform, and the reaction yield is higher. In one embodiment, in step (2), epsilon-caprolactone and the polyol are heated to be completely molten, then the catalyst is added, and the heating reaction is kept for a certain time to obtain the polycaprolactone prepolymer.

In a specific embodiment, the reaction temperature in step (2) is about 130 ℃ to about 190 ℃, e.g., about 140 ℃, about 150 ℃, about 160 ℃, about 180 ℃. Too high reaction temperature increases energy consumption in the reaction process, causes decomposition of reactants, and reduces yield of the target product; excessively low reaction temperature is disadvantageous in that the reaction occurs, the reaction rate is reduced, and the yield of the objective product is reduced.

Under the environment of inert gas, the method is favorable for reducing side reaction and maintaining the activity of the catalyst. In one embodiment, step (2) is carried out under an inert gas atmosphere. In a particular embodiment, step (2) is carried out under a nitrogen atmosphere.

The diisocyanate as described above may be used in step (3).

The ratio of the raw materials in step (3) needs to be in a suitable range in order to achieve the multicomponent reaction to produce the target branched block copolymer. Compared with polylactic acid polyether prepolymer, the use amount of polycaprolactone prepolymer is too high, so that the tensile strength of a final product is greatly reduced, and the application range of the final product is limited; too low a dosage results in a lower degree of branching of the branched block copolymer, and it is difficult to obtain a product with good properties and good fluidity. Compared with polylactic acid polyether prepolymer, the dosage of diisocyanate is too high, so that the crosslinking degree is too high, and subsequent processing is not facilitated; the use amount is too low, which causes the molecular weight of the branched block copolymer to be low, and influences various mechanical properties and processing properties. In one embodiment, the ratio of polyether prepolymer to polycaprolactone prepolymer to diisocyanate of the present invention is about 100:10 to 35:1 to 8, preferably about 100:10 to 30:1 to 5, for example about 100:30:4, about 100:22.5:5, about 100:15:4, about 100:20:4, about 100:25:5, about 100:15:2.5 by weight.

Reactive extrusion refers to a technique of simultaneously performing a chemical reaction and extrusion processing in a processing and molding apparatus (e.g., an extruder), and is also called reactive extrusion. The principle is as follows: a plasticizing extrusion system consisting of a screw and a charging barrel is used as a continuous reaction, various pre-reacted raw material components (polylactic acid polyether prepolymer, polycaprolactone prepolymer and diisocyanate in the invention) are added into the screw, and the processes of mixing, conveying, plasticizing, reacting and extruding from a die head of the raw materials are realized under the rotation of the screw. The method has the advantages of high reaction efficiency, convenient processing process, continuous large-scale production and low cost, and the process does not use or rarely uses solvents and is friendly to human bodies and environment.

The screw can play the roles of conveying, stirring, mixing, shearing and the like, and the screw extruder has the advantages of easy feeding, good dispersibility, good mixing property, controllable residence time, continuous production and the like. In one embodiment, the extruder of the present invention is a screw extruder, preferably a twin screw extruder. The rotating speed of the screw has influence on the mixing uniformity, the residence time and the like, the rotating speed of the screw is too high, the residence time of the materials is too short, the reaction is not fully carried out, and the target product is difficult to obtain; the screw rotating speed is too slow, and the production efficiency is too low. . In one embodiment, the screw speed of the extruder during extrusion is from 50 to 150 rpm.

The temperature of the extruder influences the reaction process of the raw materials, the temperature of the extruder is too high, the temperature of a raw material system is too high, degradation is easily caused, and meanwhile, the product has high fluidity at high temperature and is difficult to extrude into strips; the set temperature of the extruder is too low, the reaction speed is too slow or the reaction is not carried out, and thus the target product cannot be extruded. In one embodiment, the temperature of each zone of the extruder is 100-200 ℃. In one embodiment, the extruder head temperature of the present invention is 150-.

Performance of

Number average molecular weight (Mn): the polymer is composed of homologous mixture with same chemical composition and different polymerization degree, i.e. is composed of high polymer with different molecular chain length. The size of the molecules is usually characterized by the average molecular weight. The statistical average in terms of the number of molecules is referred to as the number average molecular weight, and the symbol is (Mn). Number average molecular weight is the sum of the molecular weights of the components x the moles of components per total moles. In the present invention, the measurement can be performed by Gel Permeation Chromatography (GPC). The number average molecular weight of the branched block copolymer of the present invention may be about 100000 or more, for example about 135000, about 126000, about 138000, about 119000, about 128000, about 136000, about 127000, about 137000.

Tensile strength: representing the resistance of the maximum uniform plastic deformation of the branched block copolymer material, wherein the deformation of a tensile sample is uniform and consistent before the tensile sample bears the maximum tensile stress, but after the maximum tensile stress exceeds the maximum uniform plastic deformation, the necking phenomenon begins to occur, namely, the concentrated deformation is generated; for brittle materials with no (or little) uniform plastic deformation, it reflects the fracture resistance of the material. The symbols are Rm in MPa. During the stretching process of the sample, after the material passes through a yield stage and enters a strengthening stage, the maximum force (F) born by the material during the breaking process is obviously reduced along with the transverse section size_b) Divided by the original cross-sectional area (S) of the sample_o) The resulting stress (σ) is referred to as the tensile strength or strength limit (σ b). It represents the maximum ability of a material to resist failure under tension. The calculation formula is as follows: σ ═ F_b/S_oIn the formula: f_bThe maximum force that the sample withstood when it was pulled apart is expressed in N (newtons); s_oRepresenting the original cross-sectional area of the sample in mm². In the present invention, the measurement can be performed by a universal tester. The branched block copolymers of the present invention have a tensile strength of about 30 to 80MPa, preferably about 35 to 75MPa, for example about 49MPa, about 47MPa, about 42MPa, about 45MPa, about 40MPa, about 43MPa, about 48 MPa.

Elongation at break: the elongation at break of the branched block copolymers of the present invention is generally expressed in terms of the relative elongation at break, i.e., the ratio of the elongation at break of the branched block copolymer fiber to its initial length, expressed as a percentage. It is an index characterizing the softness and elasticity properties of the branched block copolymer. The greater the elongation at break indicates the better the softness and elasticity, and the desired elongation at break should be provided depending on the use of the fiber. When the branched block copolymer fiber is broken by external force, the ratio of the elongation length before and after stretching to the length before stretching is called the elongation at break. In the present invention, the measurement can be performed by a universal tester. The branched block copolymers of the present invention may have an elongation at break of about 300-600%, for example about 314%, about 324%, about 408%, about 364%, about 467%, about 385%, about 323%, about 358%.

Notched impact strength: an index of the branched block copolymers of the present invention is defined as the energy absorbed per unit cross-sectional area when the sample is broken or fractured under impact load. In the present invention, the measurement can be performed by a notched impact tester. The branched block copolymer of the present invention may have a notched impact strength of about 3KJ/m or more²E.g. about 4.2KJ/m²About 3.9KJ/m²About 4.5KJ/m²About 3.7KJ/m²About 3.2KJ/m²About 3.6KJ/m²。

The melting point of the polymer refers to the temperature at which the polymer is changed from a solid state to a molten state, and the melting process of the polymer has a wide melting temperature range, namely, a melting limit exists. The temperature at which it finally melts completely is generally referred to as the melting point. The melting point can be obtained by using a differential scanning calorimeter (DSC, TA apparatus), and the temperature increase rate thereof can be, for example, 10 ℃/min. The branched block copolymers of the present invention may have a melting point of about 140 ℃ to about 190 ℃, e.g., about 162 ℃, about 165 ℃, about 163 ℃, about 169 ℃, about 170 ℃.

The melt index, also known as the melt flow index, melt flow index or melt flow index, is used to indicate the flowability of the branched block copolymer material during processing. It is defined as: the amount of thermoplastic mass extruded in a given time period, i.e.the mass of melt passing through a standard die capillary per 10min, expressed as MFR, is given in g/10min under the specified conditions. The melt flow rate can characterize the viscous flow behavior of the polymeric material in the molten state. The melt index can be measured by a melt index tester, and the specific operation process of the test is as follows: after the high molecular material to be measured is heated to a certain temperature, the upper end of the raw material is downwards extruded by a certain weight applied by a piston, and the extruded weight of the raw material within 10 minutes is measured, namely the melt index. The larger the melt index, the lower the viscosity of the polymer material. A specific test method of the invention is as follows: after heating the branched block copolymer to be measured to 190 ℃, the upper end of the branched block copolymer was pressed downward by applying a weight of 2.16kg by a plunger, and the weight of the branched block copolymer extruded within 10 minutes was measured, i.e., its melt index. The branched block copolymers of the present invention can have a melt index of about 20 to 45g/10min, for example about 35g/10min, about 32g/10min, about 38g/10min, about 37g/10min, about 33g/10min, about 36g/10min, about 30g/10 min.

The Vicat softening temperature is the temperature at which a polymer material is put in a liquid heat transfer medium and a sample is pressed into the liquid heat transfer medium by a 1-mm-square pressure needle under a certain load and a certain constant temperature. Can be measured by a thermal deformation Vicat softening point temperature measuring instrument, and the corresponding national standard is GB/T1633-2000. The Vicat softening temperature is one of indexes for evaluating the heat resistance of the material and reflecting the physical and mechanical properties of the product under the heated condition. The higher the Vicat softening temperature, the better the dimensional stability of the material when heated, the lower the thermal deformation, i.e.the better the resistance to thermal deformation, the higher the rigidity and the higher the modulus. The vicat softening temperature of the branched block copolymers of the present invention may be from about 80 to 120 ℃, e.g., about 94 ℃, about 95 ℃, about 93 ℃, about 98 ℃, about 96 ℃, about 97 ℃.

The relative viscosity, also called viscosity ratio, refers to the ratio of the viscosity of the dispersed phase to the viscosity of the continuous phase, and is used to indicate the difference between the viscosities of the two phases. Viscosity can be measured, for example, by a Ubbelohde viscometer. The branched block copolymers of the present invention may have a relative viscosity of about 1.8 to 2.5, for example about 2.3, about 2.0, about 2.4, about 2.2, about 2.1.

Advantageous effects

According to the invention, the branched block copolymer with high fluidity and high toughness is obtained by taking polylactic acid polyether prepolymer, polycaprolactone prepolymer and diisocyanate as raw materials and adopting a reaction extrusion mode. The branched block copolymer is a terpolymer of polylactic acid-polyether-polycaprolactone, has good melt fluidity on the premise of ensuring higher molecular weight, can be processed and molded at lower temperature, and avoids thermal degradation; the density of the physical cross-linking area is high, and the heat resistance is better than that of the linear polylactic acid. Meanwhile, the introduction of the polyether and polycaprolactone block provides great toughness, the defect of brittleness of polylactic acid is greatly improved, the elongation at break can reach more than 300%, the unique branched chain structure enables the polylactic acid to have good fluidity and heat resistance, and the application field of the polylactic acid is expanded.

Examples

The present invention will be described in further detail with reference to specific examples.

It should be noted that the following examples are only for clearly illustrating the technical solutions of the present invention, and are not intended to limit the present invention. It will be apparent to those skilled in the art that other variations and modifications may be made in the foregoing disclosure without departing from the spirit or essential characteristics of the invention, and it is not desired to exhaustively enumerate all embodiments, but rather those obvious variations and modifications are within the scope of the invention. Unless otherwise indicated, both the instrumentation and reagent materials used herein are commercially available.

Example 1

Example 1 was prepared by the following preparation method:

(1) 500g L-lactide and 50g polyethylene glycol with the number average molecular weight of 5000 are taken to be put in a reactor to displace nitrogen, the temperature is raised to 130 ℃ to be completely melted, 0.12g stannous octoate is added to be mixed evenly, and the mixture reacts for 5 hours at 160 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 10g of pentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 110 ℃ to ensure that the epsilon-caprolactone and the pentaerythritol are completely melted, 0.12g of stannous octoate is added, the materials are uniformly mixed and react for 5 hours at 140 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 300g of polycaprolactone prepolymer prepared in the step (2) and 50g of naphthalene diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 100 ℃, 120 ℃, 140 ℃, 160 ℃ and 180 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 120 rpm.

Example 2

Example 2 was prepared by the following preparation method:

(1) 500g L-lactide and 75g polyethylene glycol with the number average molecular weight of 8000 are taken to be arranged in a reactor, nitrogen is replaced, the temperature is raised to 130 ℃ to be completely melted, 0.2g stannous octoate is added to be evenly mixed, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 15g of pentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 120 ℃ to be completely melted, 0.2g of stannous octoate is added, the mixture is uniformly mixed, and the mixture is reacted for 5 hours at 150 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 300g of polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 160 ℃, 180 ℃ and 200 ℃ in sequence, the temperature of the extruder head is 180 ℃, and the rotating speed of the screw of the extruder is 150 rpm.

Example 3

Example 3 was prepared by the following preparation method:

(1) 500g L-lactide and 75g of polytetrahydrofuran with the number average molecular weight of 8000 are taken to be placed in a reactor, nitrogen is replaced, the temperature is raised to 140 ℃ to be completely melted, 0.3g of stannous octoate is added to be mixed evenly, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 10g of dipentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 120 ℃ to ensure that the epsilon-caprolactone and the dipentaerythritol are completely melted, 0.3g of stannous octoate is added, the mixture is uniformly mixed, and the reaction is carried out for 5 hours at 150 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 500g of polycaprolactone prepolymer prepared in the step (2) and 100g of toluene-2, 4-diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reactive extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 155 ℃, 170 ℃ and 180 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 100 rpm.

Example 4

Example 4 was prepared by the following preparation method:

(1) 500g L-lactide and 75g of polytetrahydrofuran with the number average molecular weight of 12000 are taken to be put into a reactor to displace nitrogen, the temperature is raised to 140 ℃ to be completely melted, 0.3g of zinc oxide is added to be mixed evenly, and the mixture is reacted for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 20g of dipentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 120 ℃ to ensure that the epsilon-caprolactone and the dipentaerythritol are completely melted, 0.3g of zinc oxide is added, the materials are uniformly mixed, and the reaction is carried out for 5 hours at 140 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 400g of polycaprolactone prepolymer prepared in the step (2) and 80g of toluene-2, 4-diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reactive extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 135 ℃, 150 ℃, 165 ℃ and 175 ℃ in sequence, the temperature of the extruder head is 165 ℃, and the rotating speed of the screw of the extruder is 75 rpm.

Example 5

Example 5 was prepared by the following preparation method:

(1) 500g L-lactide and 25g of polypropylene glycol with the number average molecular weight of 3000 are taken to be placed in a reactor to displace nitrogen, the temperature is raised to 150 ℃ to be completely melted, 0.3g of zinc oxide is added to be mixed evenly, and the mixture is reacted for 3 hours at 190 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 15g of tripentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 130 ℃ to be completely melted, 0.3g of zinc oxide is added, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 160 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 600g of polycaprolactone prepolymer prepared in the step (2) and 80g of toluene-2, 4-diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reactive extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 160 ℃, 170 ℃ and 175 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 100 rpm.

Example 6

Example 6 was prepared by the following preparation method:

(1) 500g L-lactide and 50g of polypropylene glycol with the number average molecular weight of 6000 are taken to be placed in a reactor to displace nitrogen, the temperature is raised to 150 ℃ to be completely melted, 0.3g of stannous chloride is added to be evenly mixed, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 20g of tripentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 130 ℃ to be completely melted, 0.3g of stannous chloride is added, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 160 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 450g of polycaprolactone prepolymer prepared in the step (2) and 100g of diphenylmethane diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 160 ℃, 170 ℃ and 175 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 100 rpm.

Example 7

Example 7 was prepared by the following preparation method:

(1) 500g D-lactide and 50g polyethylene glycol with the number average molecular weight of 10000 are taken to be put in a reactor to displace nitrogen, the temperature is raised to 150 ℃ to be completely melted, 0.3g stannous chloride is added to be mixed evenly, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 15g of pentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 130 ℃ to be completely melted, 0.3g of stannous chloride is added, the mixture is evenly mixed, and the mixture is reacted for 4 hours at 160 ℃ to prepare the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 300g of polycaprolactone prepolymer prepared in the step (2) and 80g of diphenylmethane diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 160 ℃, 170 ℃ and 175 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 100 rpm.

Example 8

Example 8 was prepared by the following preparation method:

(1) 500g D-lactide and 75g polyethylene glycol with the number average molecular weight of 10000 are taken to be put in a reactor to displace nitrogen, the temperature is raised to 150 ℃ to be completely melted, 0.3g zinc chloride is added to be mixed evenly, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 20g of pentaerythritol are taken to be placed in a reactor to replace nitrogen, the temperature is raised to 130 ℃ to ensure that the epsilon-caprolactone and the pentaerythritol are completely melted, 0.3g of zinc chloride is added, the materials are uniformly mixed, and the reaction is carried out for 4 hours at 160 ℃ to prepare the polycaprolactone prepolymer.

(3) Weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 400g of polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate respectively, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 120 ℃, 140 ℃, 160 ℃, 170 ℃ and 175 ℃ in sequence, the temperature of the extruder head is 170 ℃, and the rotating speed of the screw of the extruder is 100 rpm.

Comparative example 1

(1) Taking 500g L-lactide and 50g of polyethylene glycol with the number average molecular weight of 600 in a reactor, displacing nitrogen, heating to 130 ℃ to completely melt the mixture, adding 0.5g of stannous octoate, uniformly mixing, and reacting at 160 ℃ for 5 hours to obtain the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 5g of pentaerythritol are taken to be placed in a reactor to replace nitrogen, the temperature is raised to 110 ℃ to ensure that the epsilon-caprolactone and the pentaerythritol are completely melted, 0.5g of stannous octoate is added, the materials are uniformly mixed, and the reaction is carried out for 5 hours at 140 ℃ to prepare the polycaprolactone prepolymer.

Wherein, the molecular weight of the polyethylene glycol used in the step (1) is too low, and the branched block copolymer of the final product has poor molding and can not be formed into strips.

Comparative example 2

(1) 500g L-lactide and 50g polyethylene glycol with the number average molecular weight of 5000 are taken to be put in a reactor to displace nitrogen, the temperature is raised to 130 ℃ to be completely melted, 0.3g stannous octoate is added to be mixed evenly, and the mixture reacts for 4 hours at 180 ℃ to prepare the polylactic acid polyether prepolymer.

(2) 500g of epsilon-caprolactone and 15g of pentaerythritol are taken to be put in a reactor to replace nitrogen, the temperature is raised to 120 ℃ to ensure that the epsilon-caprolactone and the pentaerythritol are completely melted, 0.3g of stannous octoate is added, the materials are uniformly mixed and react for 5 hours at 150 ℃, and the polycaprolactone prepolymer is prepared.

(3) Respectively weighing 2000g of polylactic acid polyether prepolymer prepared in the step (1), 300g of polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate, uniformly mixing, adding into a double-screw extruder, and carrying out reaction extrusion to obtain a branched block copolymer; wherein the heating temperature of each section of the extruder from the feed inlet to the discharge outlet of the extruder head is set to be 150 ℃, 170 ℃, 190 ℃, 210 ℃ and 230 ℃ in sequence, the temperature of the extruder head is 220 ℃, and the rotating speed of the screw of the extruder is 150 rpm.

Wherein, in the reaction extrusion process in the step (3), the temperature of each area of the extruder and the temperature of the machine head are too high, and after extrusion, the branched block copolymer of the final product is poor in molding and cannot be formed into strips.

Comparative example 3

(2) 500g of epsilon-caprolactone and 100g of hydroxyl-terminated hyperbranched polyester H20 (product number: ACS1811A, brand name: Boltorn H20 Premium, number of terminal hydroxyl groups: 16) are taken to be placed in a reactor, nitrogen is replaced, the temperature is raised to 150 ℃ to be completely melted, 0.12g of stannous octoate is added, the mixture is uniformly mixed, and the mixture is reacted for 5 hours at 180 ℃ to prepare the polycaprolactone prepolymer.

Performance testing

Number average molecular weight (Mn): the test was performed using Gel Permeation Chromatography (GPC).

Tensile strength: the test was carried out by GB/T1040.2-2006 using a universal tester.

Elongation at break: the test was carried out by GB/T1040.3-2006 using a universal tester.

Notched impact strength: the test was carried out by GB/T1843-2006 using a notched impact tester.

Melting point: a differential scanning calorimeter (DSC, TA instruments) was used, and the temperature rise rate was 10 ℃/min.

Melt index: the number of grams of melt flowing out in 10min was measured at 190 ℃ under a load of 2.16kg using a melt index tester (MFI 1211).

Vicat softening temperature: the test is carried out by GB/T1633-2000 by using a thermal deformation Vicat softening point temperature tester.

Relative viscosity: the test was performed using a Ubbelohde viscometer.

Examples 1-6 were measured according to the test methods described above, and the data shown in table 1 below were obtained.

TABLE 1

As shown in the above examples and the performance data thereof, the prepared branched block copolymer is a terpolymer of polylactic acid-polyether-polycaprolactone and has a unique branched chain structure, so that the branched block copolymer has high molecular weight, good melt flowability and good heat resistance. The introduction of the polyether and polycaprolactone block provides great toughness for the branched block copolymer, the elongation at break of the branched block copolymer can reach more than 300%, and the branched block copolymer has other good mechanical properties (including high tensile strength, high notch impact strength and the like) and has wide application prospects.

In the step (2) of the comparative example 3, the hydroxyl-terminated hyperbranched polyester H20 is selected as the end-capping agent, and the prepared polycaprolactone prepolymer contains too many terminal hydroxyl groups in the structure, so that the prepared final product has too high fluidity and reduced mechanical property, and is not beneficial to use.

The above examples are merely illustrative of the preferred embodiments of the present invention and any obvious variations and modifications which would occur to persons skilled in the art without departing from the spirit of the invention are to be considered as part of the invention.

Claims

1. A branched block copolymer comprising: a branched block copolymer obtained by the reaction of a polylactic acid polyether prepolymer, a polycaprolactone prepolymer and diisocyanate, wherein,

wherein the content of the first and second substances,

n, n' are integers each independently selected from 5 to 500;

a represents a polyether moiety;

wherein the content of the first and second substances,

p is an integer selected from 40 to 500,

2. The branched block copolymer of claim 1,

the polyether moiety comprises a structure selected from the group consisting of:

wherein X is selected from a linear or branched hydrocarbon chain of 2 to 10 carbon atoms, said hydrocarbon chain being optionally substituted, each independently, with one or more substituents selected from alkyl, cycloalkyl, alkoxy, cyano, aryl and heteroaryl; m is an integer selected from 40 to 500;

preferably, the polyether moiety comprises a structure selected from the group consisting of:

wherein m is₁、m₂、m₃Are each independently selected integers from 40-500.

3. The branched block copolymer of claim 1 or 2,

each L, L' is independently selected from: c_3-20A linear or branched hydrocarbon chain of (C)_3-20The hydrocarbon chain and the ether chain are respectively and independently substituted by 2 to 10 hydroxyl groupsSubstitution;

the hydrocarbon chain and the ether chain are respectively and independently optionally substituted by one or more R^xSubstituted with the substituent(s);

the R is^xSelected from: c_3-20Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, cyano.

4. The branched block copolymer of any one of claims 1 to 3,

each of said L, L' is independently selected from the structures of the following formulae (IV-1) to (IV-4):

the C atoms in the formulas (IV-1) to (IV-4) are respectively and independently optionally selected from one or more R^xWherein, the substituent(s) of (a),

5. The branched block copolymer of any one of claims 1 to 4,

l, L' are of the same construction.

6. The branched block copolymer of any one of claims 1 to 5, wherein

The diisocyanate is aromatic diisocyanate;

preferably, the diisocyanate is selected from: 1, 5-naphthalene diisocyanate, toluene-2, 4-diisocyanate, diphenylmethane diisocyanate, and combinations thereof.

7. The branched block copolymer of any one of claims 1 to 6,

the number average molecular weight of the polylactic acid polyether prepolymer is 5000-30000, and/or

The number average molecular weight of the polycaprolactone prepolymer is 5000-

The number average molecular weight of the branched block polymer is 100000 or more.

8. A method of making the branched block copolymer of any one of claims 1-7, comprising:

step (1): lactide and polyether are reacted to prepare a polylactic acid polyether prepolymer;

step (2): reacting epsilon-caprolactone with polyhydric alcohol, and carrying out ring-opening polymerization on the epsilon-caprolactone to prepare a polycaprolactone prepolymer;

and (3): reacting and extruding the polylactic acid polyether prepolymer prepared in the step (1), the polycaprolactone prepolymer prepared in the step (2) and diisocyanate by an extruder to prepare a branched block copolymer;

wherein the polyol is one or more selected from polyols containing 3 to 11 hydroxyl groups.

9. The method of claim 8, wherein,

the number average molecular weight of the polyether used in the step (1) is 1000-20000; and/or

In the step (1), the ratio of lactide to polyether is 100:1-20 by weight; and/or

In the step (2), the proportion of the epsilon-caprolactone to the polyhydric alcohol is 100:0.5-5 by weight; and/or

In the step (3), the ratio of the polylactic acid polyether prepolymer to the polycaprolactone prepolymer to the diisocyanate is 100:10-35:1-8 by weight.

10. The method of claim 8 or 9, wherein,

in step (1) a catalyst is used, said catalyst being selected from the group consisting of: a tin-based catalyst, a zinc-based catalyst, and combinations thereof, preferably, the catalyst is selected from the group consisting of stannous octoate, stannous chloride, zinc oxide, zinc chloride, and combinations thereof; and/or

In step (2) a catalyst is used, said catalyst being selected from the group consisting of: a tin-based catalyst, a zinc-based catalyst, and combinations thereof, preferably, the catalyst is selected from the group consisting of stannous octoate, stannous chloride, zinc oxide, zinc chloride, and combinations thereof.

11. The method of any one of claims 8-10, wherein,

the reaction temperature in the step (1) is 150-210 ℃; and/or

The reaction time in the step (1) is 3-8 hours; and/or

The reaction temperature in the step (2) is 130-190 ℃; and/or

The reaction time in the step (2) is 3 to 8 hours.

12. The method of any one of claims 8-11, wherein,

in the step (3), the extruder is a double-screw extruder; and/or

The temperature of each zone of the extruder is 100-200 ℃; and/or

The temperature of the head of the extruder is 150-200 ℃; and/or

The screw rotating speed of the extruder in the extrusion process is 50-150 rpm.