CN114276511B

CN114276511B - Branched block copolymer and preparation method thereof

Info

Publication number: CN114276511B
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: 2023-08-18
Anticipated expiration: 2042-01-10
Also published as: CN114276511A

Abstract

The present invention relates to a branched block copolymer and a method for preparing the same, the branched block copolymer comprising: polylactic acid polyether prepolymer and polycaprolactoneA branched block copolymer obtained by reacting a prepolymer with a diisocyanate, wherein the polylactic acid polyether prepolymer comprises the structure of the following formula (I):wherein n, n' are integers each independently selected from 5 to 500; a represents a polyether moiety; the polycaprolactone prepolymer comprises the structure of 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, casting and 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, spinning and the like. However, it has some disadvantages in that it is a brittle material at normal temperature due to its high glass transition temperature, and at the same time, it is poor in impact resistance, thermal stability, etc. 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 the defect of 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 phenol-oxygen resin, and the phenol-oxygen resin accounts for 1-20wt% of the mass of the composite material; wherein the weight average molecular weight of the phenolic 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 flow aid, and blends hyperbranched polymer with specific structure with polylactic acid material under specific addition amount, thus obtaining 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 reacting a polylactic acid polyether prepolymer, a polycaprolactone prepolymer and diisocyanate, wherein,

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

wherein, the liquid crystal display device comprises a liquid crystal display device,

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

a represents a polyether moiety;

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

p is an integer selected from 40-500,

l, L' are each independently selected from structures containing 2 to 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 reacts with polyether to prepare polylactic acid polyether prepolymer; step (2): reacting epsilon-caprolactone with polyol, and performing ring-opening polymerization on the epsilon-caprolactone to obtain polycaprolactone prepolymer; step (3): the polylactic acid polyether prepolymer prepared in the step (1), the polycaprolactone prepolymer prepared in the step (2) and diisocyanate are subjected to reaction extrusion through an extruder to prepare a branched block copolymer; wherein the polyol is one or more polyols selected from the group consisting of 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 indicated otherwise.

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 the event of a conflict, the definitions provided herein will control.

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

When an amount, concentration, or other value or parameter is given as either a range, preferred range or upper and lower limit or a particular value, 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 range. The scope of the invention is not limited to the specific values recited when defining the scope. For example, "1-8" encompasses 1, 2, 3, 4, 5, 6, 7, 8 and any subrange comprised of any two values therein, e.g., 2-6, 3-5.

The terms "about", "about" when used in conjunction with a numerical variable generally refer to the value of the variable and all values of the variable being within experimental error (e.g., within a confidence interval of 95% for the average) or within + -10% of the specified value, or more broadly.

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. Those skilled in the art will appreciate that such terms as "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 any elements, steps, or components that are optionally present that do not materially affect the basic and novel characteristics of the claimed subject matter. It should be understood that the expression "comprising" encompasses the expressions "consisting essentially of …" and "consisting of …".

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

When numerical values or range endpoints are described herein, it is to be understood that the disclosure includes the specific value or endpoint cited.

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

Unless otherwise indicated, the terms "combination thereof" and "mixtures thereof" refer to multicomponent mixtures of the elements, e.g., two, three, four, and up to the maximum possible multicomponent mixtures.

Furthermore, the number of components or groups of components of the present invention not previously indicated is not limiting with respect to the number of occurrences (or existence) of components or groups of components. Thus, the singular forms of a component or a constituent should be interpreted to include one or at least one, and the plural unless the numerical value clearly indicates the singular.

The term "optional" or "optionally" as used herein means 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 lower and upper limits of a range of values are disclosed, any number and any range encompassed within the range are specifically disclosed. In particular, each range of values (in the form "about a to b", or equivalently, "about a-b") of values disclosed herein is understood to mean each value and range encompassed within the broader range.

For example, the expression "C _1-6 "is understood to cover any subrange therein as well as every point value, e.g. C _2-5 、C _3-4 、C ₁ - ₂ 、C _1-3 、C _1-4 、C _1-5 Etc. and C ₁ 、C ₂ 、C ₃ 、C ₄ 、C ₅ 、C ₆ Etc. For example, the expression "C _3-10 "also should be understood in a similar manner, for example, any subrange and point value contained therein may be contemplated. The expression "5-10 membered" should also be understood in a similar manner, e.g. any subrange and point value comprised therein, e.g. 5-6 membered, 5-7 membered, 5-8 membered, 5-9 membered, 5-10 membered, 6-7 membered, 6-8 membered, 6-9 membered, 6-10 membered, 7-8 membered etc. and 5, 6, 7, 8, 9, 10 membered etc.

The term "hydrocarbon chain" may refer herein to a saturated or unsaturated chain consisting only of carbon, 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 oxygen atoms.

The term "alkyl", when used herein alone or in combination with other groups, refers to a saturated straight or branched hydrocarbon group. Alkyl can be C _1-6 An alkyl group. As used herein, the term "C _1-6 Alkyl "means having 1 to 6 carbon atoms (e.g., 1, 2,3. 4, 5 or 6 carbon atoms). For example "C _1-6 The alkyl group "may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl or the like.

The term "alkoxy", when 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. Alkoxy can be C _1-6 An alkoxy group.

The term "cycloalkyl", when used herein alone or in combination with other groups, refers to a saturated hydrocarbon ring comprising a cyclic structure. Cycloalkyl groups may be C _3-8 Cycloalkyl groups. Examples thereof include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like.

The term "heterocyclyl" refers generally to aliphatic hydrocarbons containing a cyclic structure, typically having 3 to 12 ring atoms, at least 2 carbon atoms, and 1 to 3 heteroatoms independently selected from oxygen, sulfur and nitrogen. "heterocycle" also refers to a 5-to 7-membered heterocycle containing one or more heteroatoms selected from nitrogen, oxygen and sulfur fused to a 5-and 6-membered aromatic carbocyclic ring, provided that the attachment site is on the heterocycle. The heterocyclic ring may be saturated or contain one to more double bonds (i.e., partially unsaturated). The heterocycle may be substituted with oxo (oxo). The carbon or heteroatom of the heterocycle may be the attachment site, provided that a stable structure is formed. When a substituent is present on a heterocycle, the substituent may be attached to any heteroatom or carbon atom of the heterocycle provided that a stable chemical structure is formed. The heterocyclic ring and heteroaryl groups as described herein are defined as non-overlapping.

The term "aryl", when 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 _6-10 Aryl group). As used herein, the term "C _6-10 Aryl "refers to an aromatic group containing 6 to 10 carbon atoms. Examples include, but are not limited to, phenyl and naphthyl.

The term "heteroaryl", when 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, with the remaining ring atoms being 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 ring atoms), particularly 5, 6, 9, 10 ring atoms. And in each case the heteroaryl group may optionally be further benzo-fused. Examples of heteroaryl groups are, for example, thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, pyrazinyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, and the like, and the benzo derivatives thereof; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolinyl, isoquinolinyl, benzofuranyl, benzothienyl, indolyl, isoindolyl, and the like, and their benzo derivatives.

The terms "substituted" and "substituted" refer to the replacement of one or more (e.g., one, two, three, or four) hydrogens on the designated atom with a selection from the indicated group, provided that the designated atom's normal valency is not exceeded, and that the substitution forms 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 can be (1) unsubstituted or (2) substituted. If an atom or group is described as being optionally substituted with one or more of the list of substituents, then one or more hydrogens on that atom or group may be replaced with an independently selected, optional substituent. If substituents are described as "independently selected" or "each independently" then 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 substituent or substitution position or different substituents or substitution positions may be the sameOr R groups referred to by different symbols (e.g., without limitation, R ³ 、R ^a 、R ^b 、R ^c And/or R ^x ) When R is selected, R may be the same or different. The same is true for 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 it is connected to another structure through the bond. For example:meaning that the benzene ring is attached to another structure by a bond with a wavy line shown thereon.

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

When the bond of a substituent is shown as a bond through the ring connecting two atoms, then such substituent may be bonded to any ring-forming 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 "repeat unit" refers to a combination of atoms attached together in a manner on the polymer chain, which is the basic unit that makes up the 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: and (3) a branched block copolymer obtained by reacting the polylactic acid polyether prepolymer, the polycaprolactone prepolymer and diisocyanate.

Polylactic acid polyether prepolymer

wherein n, n 'represents the number of repeating units, n' is an integer independently selected from 5 to 500, for example 5, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.; a represents a polyether moiety.

By the reaction of lactide and polyether, polylactic acid polyether prepolymer can be prepared, which comprises polylactic acid part and polyether part. Hydroxyl functional groups are present at both ends of the polylactic acid polyether prepolymer, which terminal hydroxyl groups can be reacted with a diisocyanate in a subsequent step to form the final branched block copolymer.

The polylactic acid moiety can provide the end product branched block copolymer with excellent biodegradability, compatibility and absorbency, and ease of processing.

In one embodiment of the invention, n' in formula (I) is an integer independently selected from 5-500. The too long chain length of the polylactic acid part can lead to the reduced activity of the reactive groups (namely, hydroxyl groups) at the two ends of the polylactic acid polyether prepolymer, which is unfavorable for the subsequent reaction with diisocyanate; the chain length is too short, the molecular weight of the final branched block copolymer is lower, and various mechanical properties are poorer.

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

Polyethers having ether linkages in their backbone and hydroxyl functionality at both ends. The polyether participates in lactide in ring-opening polymerization through hydroxyl groups thereof, so that a polylactic acid polyether prepolymer is formed, wherein both ends of a 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 obtained by selecting corresponding polyether. In one embodiment, the structure of the polyether moiety is composed of two or more repeating units. Can be obtained by selecting corresponding block polyether.

In one embodiment of the 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 optionally each independently substituted 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, etc.

It will be appreciated that when the polyether moiety comprises a combination of two or more structures, the structures are linked by ether linkages, one possible structure of which is shown below:

Wherein X, X' are each independently selected from a linear 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 integers each independently selected from 40-500, e.g., 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.

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

wherein m is ₁ 、m ₂ 、m ₃ Are integers each independently selected from 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.

It will be appreciated that when the polyether moiety consists of two or more of formula (III-1), formula (III-2) and formula (III-3), the linkages between the structures are via ether linkages.

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

wherein m is ₁ 、m ₂ As defined above.

The polyether part has long chain length, and the hydroxyl reactivity at the two ends of the polyether part is low, so that the polyether part is unfavorable for reacting with lactide to form polylactic acid polyether prepolymer; the chain length is too short, the molecular weight of the prepared polylactic acid polyether prepolymer is low, and the molecular weight of the finally prepared branched block copolymer is low, and the mechanical properties are poor. In one embodiment, m ₁ 、m ₂ 、m ₃ Are integers each independently selected from 40-500, such as 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.

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

The molecular weight of the polylactic acid polyether prepolymer affects the reactivity with diisocyanate in the subsequent step, 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 polylactic acid polyether prepolymer has a number average molecular weight of 5000 to 30000. The molecular weight of the polylactic acid polyether prepolymer is too high, and the reactivity of hydroxyl groups at two ends of the polylactic acid polyether prepolymer is low, so that the subsequent reaction with diisocyanate is not facilitated; the molecular weight is too low, and the prepared branched block copolymer has low molecular weight and poor mechanical properties.

Polycaprolactone prepolymer

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

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

Through the reaction of epsilon-caprolactone and polyol, epsilon-caprolactone is subjected to ring-opening polymerization to prepare the polycaprolactone prepolymer. The polycaprolactone prepolymer is terminated by the corresponding structure introduced by the polyol (i.e., L, L 'in formula (II)), and the multiple hydroxyl groups contained in L, L' can serve as reaction sites for branching in subsequent reactions, thereby preparing the final product branched block copolymer.

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

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

The polycaprolactone prepolymer was at both ends (i.e. L, L' in formula (II)) of the corresponding structure introduced by the polyol. L, L' in the polycaprolactone prepolymer each independently comprises at least two hydroxyl groups as sites for branching in subsequent reactions, such that a branched block copolymer of the final product is formed with a branched structure. The number of hydroxyl groups contained in L, L' is too high and the flowability of the final branched block copolymer is too high, affecting its mechanical properties and its processability. In one embodiment, L, L' in formula (II) is a structure independently selected from the group consisting of 2-10 hydroxyl groups, e.g., each independently selected from the group consisting of 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: c (C) _3-20 Straight or branched hydrocarbon chain, C _3-20 The hydrocarbon chain, the ether chain each being independently substituted with 2 to 10 hydroxyl groups; the hydrocarbon chain and the ether chain are each independently optionally substituted with one or more groups selected from R ^x Is substituted by a substituent of (a); the R is ^x Selected from: c (C) _3-20 Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, and cyano.

In a specific embodiment, L, L' in the polycaprolactone prepolymer is each independently selected from the structures of the following formulas (IV-1) - (IV-4):

wherein the C atoms in formulae (IV-1) - (IV-4) are each independently optionally substituted with one or more groups selected from R ^x Is substituted by a substituent of (a); the R is ^x Selected from: c (C) _3-20 Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, and cyano.

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

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

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

In a specific embodiment, the polycaprolactone prepolymer has a structure according to formula (IV-2) as shown in L, L'. The polycaprolactone prepolymer can be prepared by taking dipentaerythritol as polyalcohol to participate in the reaction.

In a specific embodiment, L, L' of the polycaprolactone prepolymer is each independently selected from structures of formula (IV-3), (IV-4). The polycaprolactone prepolymers can be prepared by taking tripentaerythritol as polyalcohol to participate in the reaction.

The molecular weight of the polycaprolactone prepolymer influences the reactivity with diisocyanate in the subsequent step, the molecular weight of the final product and various mechanical properties. The molecular weight of the polycaprolactone prepolymer is too high, and the hydroxyl reactivity in the polycaprolactone prepolymer is low, so that the subsequent reaction with diisocyanate is not facilitated; the molecular weight is too low, and 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 5000-30000.

Diisocyanate (BI)

Herein, 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 branched block copolymer is obtained through copolymerization reaction.

The diisocyanate to be used is not particularly limited, and the structure thereof includes two isocyanate groups so that the copolymerization reaction proceeds smoothly. The number of isocyanate groups is too high (for example, 3 or more), and the degree of crosslinking of the copolymer obtained is too high, which is disadvantageous for subsequent processing.

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

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

Branched block copolymers

The branched block copolymer comprises: and (3) a branched block copolymer obtained by reacting the polylactic acid polyether prepolymer, the polycaprolactone prepolymer and diisocyanate.

The method comprises the steps of reacting diisocyanate with hydroxyl groups of a polylactic acid polyether prepolymer and a polycaprolactone prepolymer, taking polyhydroxy groups in the polycaprolactone prepolymer as branching sites, and copolymerizing the polylactic acid polyether prepolymer and the polycaprolactone prepolymer to finally obtain the branched block copolymer.

The branched segmented copolymer is a ternary polymer of polylactic acid-polyether-polycaprolactone, has a branched structure, has high molecular weight, good melt flowability and heat resistance, can have high molecular weight and good melt flowability, can be processed and molded at a low temperature, and avoids thermal degradation. Meanwhile, the physical crosslinking area density is high, so that the heat resistance is better. The introduction of polyether and polycaprolactone blocks provides great toughness and improves the brittleness of polylactic acid

In one embodiment, hydroxyl groups contained in the polylactic acid polyether prepolymer and polycaprolactone prepolymer structure are reacted with diisocyanate to undergo copolymerization to obtain a branched block copolymer. The branched block copolymer of the present invention has excellent properties, such as good flowability, toughness, etc., and is beneficial to subsequent processing and use.

The molecular weight of the branched block polymer affects the mechanical properties, and too low molecular weight can lead to excessive fluidity of the polymer and poor mechanical properties. In one embodiment, the branched block polymers of the present invention have a number average molecular weight of 100000 or greater, for example from about 100000 to 1000000, for example from about 135000, about 126000, about 138000, about 119000, about 128000, about 136000, about 127000, about 137000.

Preparation method

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

step (1): reacting lactide with polyether to prepare the polylactic acid polyether prepolymer;

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

step (3): and (3) carrying out reaction extrusion on 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 arbitrarily adjusted.

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 part is obtained through ring-opening polymerization reaction of lactide, and the lactide monomer configuration determines the configuration of the polylactic acid part. The last lactide monomer inserted into the living 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 L-lactide, L-lactide and (D, L) -lactide are shown below.

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 moieties can be obtained, thereby improving the properties of the branched block polymer of the final product. The proper 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 property. The polyether used in the present invention is not particularly limited. In one embodiment, the polyether used is a polyether composed 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 its own reactivity and the molecular weight of the resulting polylactic acid polyether prepolymer. The polyether has too high a molecular weight and the reactivity of hydroxyl groups at both ends thereof decreases, resulting in the increase of byproducts and the occurrence of partial blending in the reaction of step (1) (for example, a byproduct having only a polylactic acid moiety attached to one end of the polyether moiety is produced); the molecular weight is too low, which is unfavorable for improving toughness through polyether parts, and the prepared polylactic acid polyether prepolymer is too low, which is unfavorable for subsequent reaction, and the obtained final product has poor formability and cannot be used for practical application. In one embodiment of the invention, the polyether used in step (1) has a number average molecular weight of from 1000 to 20000.

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 lowering the yield of the final product. The obtained polylactic acid polyether prepolymer has too high molecular weight and too high viscosity, and is unfavorable for 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 branched block copolymer of the final product is affected. In one embodiment, in step (1), the ratio of lactide to polyether is from about 100:1 to 20, preferably from about 100:1 to 15, such as about 100:10, about 100:15, about 100:5, by weight.

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

In one embodiment, the catalyst used is selected from tin-based catalysts, zinc-based catalysts, and combinations thereof. The tin-based catalyst means a compound containing elemental tin, and 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 about 100:0.001 to 0.5 by weight, for example about 100:0.024, about 100:0.04, about 100:0.06.

The lactide and polyether are heated to be completely melted, 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, the lactide and polyether are heated to complete melting in step (1), followed by the addition of a catalyst, and after a certain period of time of the heating reaction, the polylactic acid polyether prepolymer is obtained.

In a specific embodiment, the reaction temperature in step (1) is about 150-210 ℃, such as about 160 ℃, about 180 ℃, about 190 ℃, about 150 ℃. Excessive reaction temperature can increase energy consumption in the reaction process, and can cause decomposition of reactants, so that the yield of target products is reduced; too low a reaction temperature is detrimental to the reaction, and the reaction rate decreases, resulting in a decrease in the yield of the target product.

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 a reaction time can cause incomplete reaction, too low molecular weight of the product, and reduced yield, which is unfavorable for subsequent reaction; too long a reaction time increases the energy consumption during the reaction and is liable to cause thermal degradation.

In the environment of inert gas, the side reaction is reduced, and the activity of the catalyst is maintained. In one embodiment, step (1) is performed under an inert gas atmosphere. In a specific embodiment, step (1) is performed under nitrogen.

Step (2): and (3) reacting epsilon-caprolactone with polyol, and carrying out ring-opening polymerization on the epsilon-caprolactone to obtain the polycaprolactone prepolymer.

Through the reaction of epsilon-caprolactone and polyol, epsilon-caprolactone is subjected to ring-opening polymerization to prepare the polycaprolactone prepolymer. The polycaprolactone prepolymer comprises a polyepsilon caprolactone moiety and a corresponding structure with both ends introduced through a polyol.

The polycaprolactone prepolymer prepared by selecting proper polyol has good reactivity and proper branching site, so that the branched block polymer of the final product has excellent performance. The polyol selected for use in the present invention is not particularly limited and contains at least 3 hydroxyl groups. As sites for branching in subsequent reactions. Too high a number of hydroxyl groups contained in the polyol can cause excessive polymer flowability, adversely affecting both mechanical properties and processability. In one embodiment, the polyols of the present invention comprise 3 to 11 hydroxyl groups, for example comprising 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 (C) _3-20 Straight or branched hydrocarbon chain, C _3-20 And each independently substituted with 2 to 10 hydroxyl groups; wherein the hydrocarbon chain, the ether chain are each independently optionally substituted with one or more groups selected from R ^x Is substituted by a substituent of (a); r is R ^x Selected from: c (C) _3-20 Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogenPlain, 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, step (2) is performed using two or more polyols.

In one embodiment, step (2) is performed using a single polyol.

In step (1), the ratio of epsilon-caprolactone to polyol affects the acquisition of the target polycaprolactone prepolymer. When the ratio of epsilon-caprolactone to polyol is too low, the formation of by-products is increased, thereby making it impossible to obtain the final product or lowering the yield of the final product. The obtained polycaprolactone prepolymer may have too high molecular weight and too high viscosity, which is disadvantageous for the subsequent reaction. When the ratio of epsilon-caprolactone to polyol is too high, the molecular weight of the prepared polycaprolactone prepolymer is too low, and the mechanical properties and processability of the final product are affected. In one embodiment, in step (2), the ratio of epsilon-caprolactone to polyol is from about 100:0.5 to 5, such as 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 catalyst is added to accelerate the rate of ring-opening polymerization reaction, wherein the proper catalyst can effectively accelerate the rate of reaction, the reaction is not affected by the chemical properties of the catalyst, such as acidity, alkalinity, oxidability, reducibility and the like, and the proper catalyst can avoid side reaction 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 epsilon caprolactone to catalyst ratio in step (2) is about 100:0.001 to 0.5 by weight, such as about 100:0.024, about 100:0.04, about 100:0.06.

And the epsilon-caprolactone and the polyol are heated to be completely melted, 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, the epsilon-caprolactone and the polyol are heated to be completely melted in the step (2), and then a catalyst is added, and after the heating reaction is maintained for a certain period of time, the polycaprolactone prepolymer is obtained.

In a specific embodiment, the reaction temperature in step (2) is about 130 to 190 ℃, such as about 140 ℃, about 150 ℃, about 160 ℃, about 180 ℃. Excessive reaction temperature can increase energy consumption in the reaction process, and can cause decomposition of reactants, so that the yield of target products is reduced; too low a reaction temperature is detrimental to the reaction, and the reaction rate decreases, resulting in a decrease in the yield of the target product.

In the environment of inert gas, the side reaction is reduced, and the activity of the catalyst is maintained. In one embodiment, step (2) is performed under an inert gas atmosphere. In a specific embodiment, step (2) is performed under nitrogen.

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

The ratio of the raw materials in step (3) needs to be within a suitable range in order to achieve a multicomponent reaction to produce the target branched block copolymer. Compared with the polylactic acid polyether prepolymer, the excessive use level of the polycaprolactone prepolymer can lead to the great reduction of the tensile strength of the final product and limit the application range of the final product; too low an amount will result in a branched block copolymer with a low degree of branching, and it is difficult to obtain a product with good properties and good flowability. Compared with the polylactic acid polyether prepolymer, the excessive use level of diisocyanate can cause too high crosslinking degree, which is unfavorable for subsequent processing; too low an amount can result in a branched block copolymer with a lower molecular weight, affecting various mechanical properties and processability. In one embodiment, the ratio of polyether prepolymer to polycaprolactone prepolymer to diisocyanate of the invention is from about 100:10 to 35:1 to 8, preferably from about 100:10 to 30:1 to 5, such as 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 in which chemical reactions and extrusion processes are simultaneously carried out in a processing-forming apparatus (e.g., an extruder), also referred to as reactive extrusion. The principle is basically as follows: the plasticizing extrusion system consisting of a screw and a charging barrel is used as a continuous reaction, various pre-reacted raw material components (the polylactic acid polyether prepolymer, the polycaprolactone prepolymer and the diisocyanate) are added into the screw, and the processes of mixing, conveying, plasticizing, reacting and extruding from a die head among the raw materials are realized under the rotation of the screw. Has the advantages of high reaction efficiency, convenient processing process, continuous mass production and low cost, and the process uses no or little solvent, thus being friendly to human body and environment.

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

The temperature of the extruder influences the reaction process of the raw materials, the extruder is excessively high in setting temperature, the raw material system is excessively high in temperature, degradation is easy to cause, and meanwhile, the product has high fluidity at high temperature and is difficult to extrude into strips; the extruder is set at too low a temperature, and the reaction rate is too slow or no reaction is performed, so that the target product cannot be extruded. In one embodiment, the temperature of each zone of the extruder is from 100 to 200 ℃. In one embodiment, the extruder of the present invention has a head temperature of 150 to 200 ℃.

Performance of

Number average molecular weight (Mn): the polymer is composed of a homologous mixture of identical chemical composition and varying degrees of polymerization, i.e. of a mixture of polymers of different molecular chain lengths. The size of the molecules is usually characterized by an average number of molecules. The number average molecular weight is referred to as the number average molecular weight, and is denoted by (Mn). Number average molecular weight = sum of the molecular weights of the components x the number of moles of component/total number of moles. In the present invention, it can be measured by Gel Permeation Chromatography (GPC). The branched block copolymers of the present invention may have a number average molecular weight of about 100000 or greater, for example about 135000, about 126000, about 138000, about 119000, about 128000, about 136000, about 127000, about 137000.

Tensile strength: representing the maximum uniform plastic deformation resistance of the branched block copolymer material, wherein the deformation of the tensile sample is uniform before the tensile sample is subjected to the maximum tensile stress, but necking phenomenon begins to appear after the tensile sample is exceeded, namely concentrated deformation is generated; for brittle materials that do not (or very little) uniformly plastically deform, it reflects the fracture resistance of the material. The symbol Rm, in MPa. During the stretching process of the sample, the material enters into strong after the yield stageThe maximum force (F) applied during breaking is significantly reduced with the transverse cross-sectional dimension after the transition stage _b ) Divided by the original cross-sectional area of the sample (S _o ) The resulting stress (σ), referred to as the tensile strength or strength limit (σb). It represents the maximum ability of a material to resist failure under tension. The calculation formula is as follows: sigma=f _b /S _o Wherein: f (F) _b The maximum force applied when the test specimen breaks is expressed in N (newtons); s is S _o Represents the original cross-sectional area of the sample in mm ² . In the 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 48MPa.

Elongation at break: the elongation at break of the branched block copolymers of the present invention is generally expressed in percent as the relative elongation at break, i.e., the ratio of the elongation at break of the branched block copolymer fiber to its initial length. It is an indicator of the softness and elasticity properties of the branched block copolymer. The larger the elongation at break means the better its softness and elasticity, and should have the desired elongation at break depending on the use of the fiber. When the branched block copolymer fiber is broken by an external force, the ratio of the elongation before and after stretching to the elongation before stretching is called elongation at break. In the 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 for measuring the branched block copolymer of the present invention is defined as the energy absorbed per cross-sectional area when the sample breaks or breaks under impact load. In the invention, the measurement can be performed by a notch impact tester. The branched block copolymers of the present invention may have a notched impact strength of about 3KJ/m or greater ² For example about 4.2KJ/m ² About 3.9KJ/m ² About 4.5KJ/m ² About 3.7KJ/m ² About 3.2KJ/m ² About 3.6KJ/m ² 。

The melting point of a polymer refers to the temperature at which it changes from a solid state to a molten state, and the melting process of the polymer exhibits a broader melting temperature range, i.e., there is a "melting limit". The temperature at which it eventually melts completely is generally referred to as the melting point. The melting point may be obtained by using a differential scanning calorimeter (DSC, TA instrument) and the temperature rise rate may be, for example, 10℃per minute. The branched block copolymers of the present invention may have a melting point of about 140 to 190 ℃, such as about 162 ℃, about 165 ℃, about 163 ℃, about 169 ℃, about 170 ℃.

Melt index, also known as melt flow index, or melt flow index, is used to indicate the flowability of a branched block copolymer material when processed. It is defined as: the amount of thermoplastic material extruded over a period of time, i.e. the mass of melt passing through a standard die capillary every 10min, is expressed as MFR in g/10min under the specified conditions. The melt flow rate can characterize the viscous flow characteristics 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 polymer material to be measured is heated to a certain temperature, the upper end of the raw material is downwards extruded by a piston under a certain weight, and the extruded weight of the raw material within 10 minutes is measured to obtain the melt index. The higher the melt index, the lower the viscosity of the polymer material. The specific test method of the invention comprises the following steps: after the branched block copolymer to be detected is heated to 190 ℃, the upper end of the branched block copolymer is downwards extruded by a piston under the weight of 2.16kg, and the extruded weight of the branched block copolymer within 10 minutes is measured to obtain the melt index. The branched block copolymers of the present invention may have a melt index of about 20 to about 45g/10min, for example about 35g/10min, about 32g/10min, about 38g/10min, about 37g/10min, about 33g/10min, about 36g/10min, about 30g/10min.

The vicat softening temperature is a temperature at which a sample is pressed into 1 mm by a 1 mm square syringe needle under a constant load and a constant temperature rise by placing a polymer material in a liquid heat transfer medium. The thermal deformation Vicat softening point temperature measuring instrument can be used for measuring, and the corresponding national standard is GB/T1633-2000. The Vicat softening temperature is one of indexes for evaluating heat resistance of materials and reflecting physical and mechanical properties of products under the heated condition. The higher the Vicat softening temperature, the better the dimensional stability of the material when heated, the less the thermal deformation, i.e. the better the heat distortion resistance, the greater 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 ℃, such as about 94 ℃, about 95 ℃, about 93 ℃, about 98 ℃, about 96 ℃, about 97 ℃.

The relative viscosity, also known as the viscosity ratio, refers to the ratio of the bulk phase viscosity to the continuous phase viscosity, and is used to represent the difference in viscosity of the two phases. The viscosity can be measured, for example, by an 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

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

Examples

The following describes the aspects of the invention in further detail with reference to specific examples.

It should be noted that the following examples are only examples for clearly illustrating the technical solution of the present invention, and are not limiting. Other variations or modifications of the above description will be apparent to those of ordinary skill in the art, and it is not necessary or exhaustive of all embodiments, and obvious variations or modifications of the invention are intended to be within the scope of the invention. The instrumentation and reagent materials used herein are commercially available unless otherwise indicated.

Example 1

Example 1 was prepared by the following preparation method:

(1) Taking 500g L-lactide and 50g of polyethylene glycol with the number average molecular weight of 5000 in a reactor, replacing nitrogen, heating to 130 ℃ to completely melt the polyethylene glycol, adding 0.12g of stannous octoate, uniformly mixing, and reacting for 5 hours at 160 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 10g of pentaerythritol in a reactor, replacing nitrogen, heating to 110 ℃ to enable the mixture to be completely melted, adding 0.12g of stannous octoate, uniformly mixing, and reacting for 5 hours at 140 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 300g of the polycaprolactone prepolymer prepared in the step (2) and 50g of naphthalene diisocyanate, uniformly mixing, and adding into a double-screw extruder for reaction extrusion to prepare 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 ℃, 180 ℃, the temperature of the extruder head is 170 ℃, and the screw speed of the extruder head is 120rpm.

Example 2

Example 2 was prepared by the following preparation method:

(1) Taking 500g L-lactide and 75g polyethylene glycol with number average molecular weight of 8000 in a reactor, replacing nitrogen, heating to 130 ℃ to completely melt, adding 0.2g stannous octoate, uniformly mixing, and reacting for 4 hours at 180 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 15g of pentaerythritol in a reactor, replacing nitrogen, heating to 120 ℃ to enable the mixture to be completely melted, adding 0.2g of stannous octoate, uniformly mixing, and reacting for 5 hours at 150 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 300g of the polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate, uniformly mixing, and adding into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 180 ℃ of the temperature of the extruder head and 150rpm of the screw speed of the extruder.

Example 3

Example 3 was prepared by the following preparation method:

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

(2) Taking 500g of epsilon-caprolactone and 10g of dipentaerythritol in a reactor, replacing nitrogen, heating to 120 ℃ to enable the dipentaerythritol to be completely melted, adding 0.3g of stannous octoate, uniformly mixing, and reacting for 5 hours at 150 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 500g of the polycaprolactone prepolymer prepared in the step (2), uniformly mixing the components, and adding the components into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 155 ℃, 170 ℃, 180 ℃, the temperature of the extruder head is 170 ℃, and the screw speed of the extruder is 100rpm.

Example 4

Example 4 was prepared by the following preparation method:

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

(2) Taking 500g of epsilon-caprolactone and 20g of dipentaerythritol in a reactor, replacing nitrogen, heating to 120 ℃ to enable the dipentaerythritol to be completely melted, adding 0.3g of zinc oxide, uniformly mixing, and reacting for 5 hours at 140 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 400g of the polycaprolactone prepolymer prepared in the step (2), uniformly mixing the components, and adding the components into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 135 ℃, 150 ℃, 165 ℃, 175 ℃, 165 ℃ of the extruder head temperature and 75rpm of the screw of the extruder head.

Example 5

Example 5 was prepared by the following preparation method:

(1) Taking 500g L-lactide and 25g of polypropylene glycol with the number average molecular weight of 3000 in a reactor, replacing nitrogen, heating to 150 ℃ to completely melt the polypropylene glycol, adding 0.3g of zinc oxide, uniformly mixing, and reacting for 3 hours at 190 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 15g of tripentaerythritol in a reactor, replacing nitrogen, heating to 130 ℃ to enable the tripentaerythritol to be completely melted, adding 0.3g of zinc oxide, uniformly mixing, and reacting for 4 hours at 160 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 600g of the polycaprolactone prepolymer prepared in the step (2), and 80g of toluene-2, 4-diisocyanate, uniformly mixing, and adding into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 100rpm of the screw of the extruder.

Example 6

Example 6 was prepared by the following preparation method:

(1) Taking 500g L-lactide and 50g of polypropylene glycol with the number average molecular weight of 6000 in a reactor, replacing nitrogen, heating to 150 ℃ to completely melt the polypropylene glycol, adding 0.3g of stannous chloride, uniformly mixing, and reacting for 4 hours at 180 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 20g of tripentaerythritol in a reactor, replacing nitrogen, heating to 130 ℃ to enable the tripentaerythritol to be completely melted, adding 0.3g of stannous chloride, uniformly mixing, and reacting for 4 hours at 160 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 450g of the polycaprolactone prepolymer prepared in the step (2), uniformly mixing the two components, and adding the mixture into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 100rpm of the screw of the extruder.

Example 7

Example 7 was prepared by the following preparation method:

(1) Taking 500g D-lactide and 50g of polyethylene glycol with the number average molecular weight of 10000 in a reactor, replacing nitrogen, heating to 150 ℃ to completely melt the polyethylene glycol, adding 0.3g of stannous chloride, uniformly mixing, and reacting for 4 hours at 180 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 15g of pentaerythritol in a reactor, replacing nitrogen, heating to 130 ℃ to enable the mixture to be completely melted, adding 0.3g of stannous chloride, uniformly mixing, and reacting for 4 hours at 160 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 300g of the polycaprolactone prepolymer prepared in the step (2), uniformly mixing the components, and adding the components into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 100rpm of the screw of the extruder.

Example 8

Example 8 was prepared by the following preparation method:

(1) Taking 500g D-lactide and 75g polyethylene glycol with the number average molecular weight of 10000 in a reactor, replacing nitrogen, heating to 150 ℃ to completely melt, adding 0.3g zinc chloride, uniformly mixing, and reacting for 4 hours at 180 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 20g of pentaerythritol in a reactor, replacing nitrogen, heating to 130 ℃ to enable the mixture to be completely melted, adding 0.3g of zinc chloride, uniformly mixing, and reacting for 4 hours at 160 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 400g of the polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate, uniformly mixing, and adding into a double-screw extruder for reaction extrusion to prepare 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 120 ℃, 140 ℃, 160 ℃, 170 ℃, 175 ℃, 170 ℃ and 100rpm of the screw of the extruder.

Comparative example 1

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

(2) Taking 500g epsilon-caprolactone and 5g pentaerythritol in a reactor, replacing nitrogen, heating to 110 ℃ to completely melt the caprolactone, adding 0.5g stannous octoate, uniformly mixing, and reacting for 5 hours at 140 ℃ to obtain 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 is poor in molding and cannot be formed into strips.

Comparative example 2

(1) Taking 500g L-lactide and 50g of polyethylene glycol with the number average molecular weight of 5000 in a reactor, replacing nitrogen, heating to 130 ℃ to completely melt the polyethylene glycol, adding 0.3g of stannous octoate, uniformly mixing, and reacting for 4 hours at 180 ℃ to obtain the polylactic acid polyether prepolymer.

(2) Taking 500g of epsilon-caprolactone and 15g of pentaerythritol in a reactor, replacing nitrogen, heating to 120 ℃ to enable the mixture to be completely melted, adding 0.3g of stannous octoate, uniformly mixing, and reacting for 5 hours at 150 ℃ to obtain the polycaprolactone prepolymer.

(3) Respectively weighing 2000g of the polylactic acid polyether prepolymer prepared in the step (1) and 300g of the polycaprolactone prepolymer prepared in the step (2) and 80g of naphthalene diisocyanate, uniformly mixing, and adding into a double-screw extruder for reaction extrusion to prepare 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 150 ℃, 170 ℃, 190 ℃, 210 ℃, 230 ℃, 220 ℃ of the temperature of the extruder head and 150rpm of the screw speed of the extruder head.

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, product name: boltorn H20 Premium, terminal hydroxyl number: 16) are taken and placed in a reactor, nitrogen is replaced, the temperature is raised to 150 ℃ to enable the mixture 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: testing was performed by GB/T1040.2-2006 using a universal tester.

Elongation at break: the test was performed 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: differential scanning calorimeter (DSC, TA instrument) was used with a temperature rise rate of 10℃per minute.

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

Vicat softening temperature: the thermal deformation Vicat softening point temperature tester is used for testing by GB/T1633-2000.

Relative viscosity: the test was performed using an 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 branched block copolymer is a ternary polymer of polylactic acid-polyether-polycaprolactone, and has a unique branched structure, so that the branched block copolymer has high molecular weight, good melt fluidity and good heat resistance. The introduction of polyether and polycaprolactone blocks provides the branched block copolymer with great toughness, the elongation at break of the branched block copolymer can reach more than 300 percent, and the branched block copolymer also has other good mechanical properties (including high tensile strength, high notch impact strength and the like) and has wide application prospect.

In the step (2) of the comparative example 3, hydroxyl-terminated hyperbranched polyester H20 is selected as a capping agent, and the prepared polycaprolactone prepolymer contains excessive hydroxyl-terminated groups in the structure, so that the prepared final product has high fluidity and reduced mechanical properties, and is unfavorable for use.

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

Claims

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

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

a represents a polyether moiety;

the polycaprolactone prepolymer comprises the structure of formula (II):

p is an integer selected from 40-500,

2. The branched block copolymer of claim 1, wherein,

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 optionally each independently substituted with one or more substituents selected from alkyl, cycloalkyl, alkoxy, cyano, aryl and heteroaryl; m is an integer selected from 40-500.

3. The branched block copolymer of claim 2, wherein,

wherein m is ₁ 、m ₂ 、m ₃ Are integers each independently selected from 40 to 500.

4. The branched block copolymer of claim 1, wherein,

the L, L' are each independently selected from: c (C) _3-20 Straight or branched hydrocarbon chain, C _3-20 The hydrocarbon chain, the ether chain each being independently substituted with 2 to 10 hydroxyl groups;

the hydrocarbon chain and the ether chain are each independently optionally substituted with one or more groups selected from R ^x Is substituted by a substituent of (a);

the R is ^x Selected from: c (C) _3-20 Cycloalkyl, heterocyclyl, aryl, heteroaryl, alkoxy, halogen, carboxyl, ester, and cyano.

5. The branched block copolymer of claim 1, wherein,

the L, L' are each independently selected from the structures of the following formulas (IV-1) - (IV-4):

the C atoms in the formulae (IV-1) to (IV-4) are each independently optionally substituted with one or more groups selected from R ^x Wherein, the substituent is substituted by a substituent group,

6. The branched block copolymer of claim 1, wherein,

the L, L' is the same structure.

7. The branched block copolymer of claim 1, wherein

The diisocyanate is an aromatic diisocyanate.

8. The branched block copolymer of claim 7, wherein the diisocyanate is selected from the group consisting of: 1, 5-naphthalene diisocyanate, toluene-2, 4-diisocyanate, diphenylmethane diisocyanate, and combinations thereof.

9. The branched block copolymer of any of claim 1-8, wherein,

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

The polycaprolactone prepolymer has a number average molecular weight of 5000-30000, and/or

The branched block polymer has a number average molecular weight of 100000 or more.

10. A method of preparing the branched block copolymer of any of claims 1-9, comprising:

step (1): lactide reacts with polyether to prepare polylactic acid polyether prepolymer;

step (2): reacting epsilon-caprolactone with polyol, and performing ring-opening polymerization on the epsilon-caprolactone to obtain polycaprolactone prepolymer;

Step (3): the polylactic acid polyether prepolymer prepared in the step (1), the polycaprolactone prepolymer prepared in the step (2) and diisocyanate are subjected to reaction extrusion through an extruder to prepare a branched block copolymer;

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

11. The method of claim 10, wherein the step of,

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

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

In the step (2), the ratio of epsilon-caprolactone to polyol 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.

12. The method of claim 10, wherein the step of,

using a catalyst in step (1), said catalyst being selected from the group consisting of: tin-based catalysts, zinc-based catalysts, and combinations thereof; and/or

Using a catalyst in step (2), said catalyst selected from the group consisting of: tin-based catalysts, zinc-based catalysts, and combinations thereof.

13. The method of claim 12, wherein the step of,

the catalyst used in step (1) is selected from stannous octoate, stannous chloride, zinc oxide, zinc chloride, and combinations thereof.

14. The method of claim 12, wherein the step of,

the catalyst used in step (2) is selected from stannous octoate, stannous chloride, zinc oxide, zinc chloride, and combinations thereof.

15. The method of claim 10, wherein the step of,

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 3-8 hours.

16. The method of claim 10, wherein the step of,

in the step (3), the extruder is a twin-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 speed of the extruder during the extrusion process was 50-150rpm.