CN107793713B

CN107793713B - Thermoplastic cellulose and aliphatic copolyester blend film and preparation method thereof

Info

Publication number: CN107793713B
Application number: CN201610805987.3A
Authority: CN
Inventors: 詹姆斯·洪学·王; 周炳; 贾钦
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2016-09-06
Filing date: 2016-09-06
Publication date: 2020-10-16
Anticipated expiration: 2036-09-06
Also published as: CN107793713A

Abstract

The invention relates to a thermoplastic film of a blend of thermoplastic cellulose and aliphatic copolyester, which mainly solves the technical problems that the application field of the thermoplastic film is limited due to high viscosity, poor film forming property and poor film stretchability in the low-temperature processing process of the thermoplastic cellulose in the prior art. The invention adopts a blend consisting of 20 to 80 mass percent of thermoplastic cellulose and 80 to 20 mass percent of aliphatic copolyester, the blend is prepared by a continuous melt extrusion blending method, and the melt viscosity of the blend is 100s at a low shear rate^‑1At least about 30% lower than the theoretical value of the additive blend of the two starting materials under the conditions; at high shear rate 1363s^‑1The technical proposal that the theoretical value of blending addition of the two starting materials is at least 30 percent lower under the condition better solves the problem and can be used for the industrial production of thermoplastic film products.

Description

Thermoplastic cellulose and aliphatic copolyester blend film and preparation method thereof

Technical Field

The invention belongs to the field of blend materials of thermoplastic cellulose and aliphatic copolyester, and particularly relates to a blend film of thermoplastic cellulose and aliphatic copolyester with special rheological properties, and a method for preparing the blend film of thermoplastic cellulose and aliphatic copolyester with special rheological properties.

Technical Field

Cellulose is the most abundant organic polymer on earth and also the most renewable biomass material every year. Cellulose is the structural material in the cell wall of green plants, woody plants contain about 30-40% cellulose, and cotton fibers contain about 90% cellulose. The main industrial uses of cellulose are paper and board, with a small amount of cellulose being used for the preparation of regenerated cellulose such as cellulophenol (Cellophane), viscose (Rayon) and some cellulose derivatives.

Since cellulose is a natural polymer obtained by converting carbon dioxide and water in the atmosphere into carbon dioxide and water by photosynthesis, carbon element in cellulose is a recently fixed carbon and is different from fossil fuels such as petroleum and coal and petrochemicals thereofThe carbon element fixed millions of years ago in the product can pass through the carbon element fixed in different periods¹⁴And C isotope calibration method. Due to the differences, the bio-based polymer material prepared based on the biomass raw material has the advantage of low carbon of the raw material compared with the petroleum-based polymer material, and the green low-carbon polymer material can be produced by adopting the production process with low energy consumption and low carbon emission. In view of such considerations, natural polymers, including cellulose, hemicellulose, lignin, starch, chitin, etc., and their derivatives, have been receiving increasing attention and research and development globally to develop high-quality green, low-carbon, and environmentally-friendly products. The wide application of the green low-carbon products confirmed by Life Cycle Assessment (Life Cycle Assessment) is helpful for supporting green production and green Life style, and contributes to reducing the content of greenhouse effect gases (carbon dioxide and the like) in the atmosphere and relieving global climate change.

Although cellulose has the advantage of low carbon in raw materials, the amount of cellulose used as plastic film is small because cellulose does not have thermoplastic properties due to its thermal decomposition temperature below its melting point. In order to overcome the defect of cellulose, researchers have developed regenerated cellulose produced by a solution method, i.e. cellulose or a cellulose derivative is dissolved in a solvent, and is processed and formed by the solution to be prepared into a film or is converted into cellulose after spinning, and viscose in the textile industry is prepared by the method.

In addition, the cellulose derivative has a low melting or plasticizing temperature after sufficient chemical transformation of the three hydroxyl groups on each repeating glucose unit, can be subjected to limited thermoplastic processing to form thermoplastic cellulose, and the materials comprise cellulose ester and cellulose ether with a certain degree of substitution. Because the yield and the product variety of the cellulose derivatives are limited, the viscosity of the industrialized products is higher, and is particularly obvious at lower processing temperature, and the products are not suitable for processing methods needing low melt viscosity, such as spinning, injection molding and the like; cellulose esters and cellulose ethers are currently used in large part as additives in the field of coatings or adhesives [ gayal, manoming, biomass materials and applications, 2008 ]. Therefore, from the viewpoint of processing applications, there is a technical need to develop a thermoplastic cellulose derivative having a low viscosity and good processability to meet the market demand of the relevant raw materials.

Until now, no document has reported the specific rheological behavior of blends of thermoplastic cellulose and aliphatic copolyester, and no method has been provided in the prior art for effectively reducing the melt viscosity of blends of thermoplastic cellulose and aliphatic copolyester, so that the application of such blends has been limited.

The invention discloses a continuous melt extrusion method for effectively reducing the melt viscosity of a blend of thermoplastic cellulose and aliphatic copolyester, discovers unexpected phenomena and results, discloses a blend composition with special rheological properties, and successfully applies the blend to the field of films.

Disclosure of Invention

One of the technical problems solved by the invention is that the melt viscosity of the blend of the thermoplastic cellulose and the aliphatic copolyester is too high in the prior art and cannot be applied to the preparation of a film with low melt viscosity, and the blend material adopted by the film can effectively reduce the viscosity of the blend to be lower than the theoretical viscosity of the blend of the thermoplastic cellulose and the starting material of the aliphatic copolyester unexpectedly; the blend has the processing performance of preparing a casting film at a lower temperature, is superior to the similar blend in the prior art, and can save more energy in the processing process due to the low melt viscosity of the blend.

The second technical problem to be solved by the present invention is to provide a process for preparing thermoplastic films of blends of thermoplastic cellulose and aliphatic copolyester having specific rheological properties corresponding to the first technical problem, the melt viscosity of the blends obtained by the process being 100s at low shear rate^-1At least about 30% lower than the theoretical value of the additive blend of the two starting materials under the conditions; at high shear rate 1363s^-1Under the condition of the two starting materials, the blending addition theoretical valueAt least 30% lower.

In order to solve one of the above technical problems, the technical scheme adopted by the invention is as follows: a film of a blend of a thermoplastic cellulose and an aliphatic copolyester having specific rheological properties, the film comprising a blend comprising from 20% to 80% by mass of a thermoplastic cellulose and from 80% to 20% by mass of an aliphatic copolyester, characterized in that the melt viscosity of the blend is 100s at a low shear rate^-1At least about 30% lower than the theoretical value of the additive blend of the two starting materials under the conditions; at high shear rate 1363s^-1Under the condition, the addition ratio is at least 30 percent lower than the blending addition theoretical value of the two raw materials; wherein the thermoplastic cellulose is selected from cellulose esters formed by cellulose and at least two organic acids, and the total number of carbon atoms of the organic acids is more than or equal to 6.

In the technical scheme, the two starting materials refer to thermoplastic cellulose and aliphatic copolyester.

In the technical scheme, the Young modulus of the blend film is more than 220MPa, the breaking strength is more than 10MPa, and the breaking elongation is more than 60%.

In the above technical solution, the substitution degree of the thermoplastic cellulose is preferably greater than 1.0; more suitable cellulose derivatives have a degree of substitution of more than 1.5, particularly suitable cellulose derivatives have a degree of substitution of more than 2.0.

In the above-mentioned embodiment, the thermoplastic cellulose is preferably cellulose acetate butyrate ester, cellulose acetate valerate ester, cellulose acetate caproate ester, cellulose acetate enanthate ester, cellulose acetate caprylate ester, cellulose acetate pelargonate ester, cellulose acetate caprate ester, cellulose acetate laurate ester, cellulose acetate palmitate ester, cellulose acetate stearate ester, cellulose propionate butyrate ester, cellulose propionate valerate ester, cellulose propionate caproate ester, cellulose propionate enanthate ester, cellulose propionate caprylate ester, cellulose propionate pelargonate ester, cellulose propionate caprate ester, cellulose propionate laurate ester, cellulose propionate stearate ester, or the like.

In the above technical solution, the aliphatic copolyester is preferably a copolyester obtained by condensing at least two α, ω -aliphatic diacids or derivatives thereof with an aliphatic diol; the aliphatic diacid is preferably at least two alpha, omega-aliphatic diacids having from 2 to 22 backbone carbon atoms, including: oxalic acid, 1, 3-malonic acid, succinic acid (1, 4-succinic acid), glutamic acid (1, 5-glutaric acid), adipic acid (1, 6-adipic acid), 1, 7-pimelic acid, 1, 8-suberic acid, 1, 9-azelaic acid, 1, 10-sebacic acid, and up to a carbon number of 22 dibasic acids; the derivatives of the aliphatic diacids include anhydrides, esters, acid halides, and the like prepared from the above diacids.

In the above technical solution, the aliphatic diacid is preferably an aliphatic diacid containing a substituent group; the substituent is preferably straight-chain alkyl, branched-chain alkyl, cyclic alkyl or alkyl with an unsaturated structure; and dibasic acids with other substituents such as cyclohexyl.

In the above technical scheme, the aliphatic diol suitable for preparing the aliphatic copolyester of the present invention includes ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 4-pentanediol, 1, 5-pentanediol, 1, 2-hexanediol, 1, 3-hexanediol, 1, 4-hexanediol, 1, 5-hexanediol, 1, 6-hexanediol, 1, 2-heptanediol, 1, 3-heptanediol, 1, 4-heptanediol, 1, 5-heptanediol, 1, 6-heptanediol, 1, 7-heptanediol, 1, 2-octanediol, 1, 3-octanediol, 1, 4-octanediol, 1, 5-octanediol, 1, 6-octanediol, 1, 7-octanediol, 1, 8-octanediol, 1, 2-nonanediol, 1, 3-nonanediol, 1, 4-nonanediol, 1, 5-nonanediol, 1, 6-nonanediol, 1, 7-nonanediol, 1, 8-nonanediol, 1, 9-nonanediol, 1, 2-decanediol, 1, 3-decanediol, 1, 4-decanediol, 1, 5-decanediol, 1, 6-decanediol, 1, 7-decanediol, 1, 8-decanediol, 1, 9-decanediol, 1, 10-decanediol up to a carbon number of 24 and diols with other substituents such as cyclohexyl.

In the above technical solution, the aliphatic copolyester is preferably: at least one of polyethylene glycol oxalate succinate, polyethylene glycol succinate, polyethylene glycol succinate glutarate, polyethylene glycol succinate adipate, polyethylene glycol glutarate adipate, polyethylene glycol suberate, polypropylene glycol malonate oxalate, polypropylene glycol succinate, polyethylene glycol succinate adipate, polyethylene glycol glutarate adipate, polyethylene glycol malonate oxalate, polyethylene glycol succinate adipate, polyethylene glycol glutarate adipate, polyethylene glycol succinate adipate, polyethylene glycol glutarate adipate, polyethylene glycol succinate adipate, and the like.

In the above embodiment, the melt index of the blend is at least about 20% higher than the theoretical value of the blend addition of the two starting materials.

In the technical scheme, the thermoplastic cellulose is preferably cellulose acetate butyrate, the thermoplastic cellulose and the aliphatic copolyester have a synergistic interaction effect, the blend of the two has the special rheological property, and the cellulose acetate butyrate is found to have better compatibility than other common thermoplastic celluloses (such as cellulose acetate, cellulose acetate propionate and the like) when being blended with the copolyester, namely, the problem of poor compatibility of the thermoplastic cellulose and the aliphatic copolyester is well solved, the compatibility of the two is good, the application range of the starting material can be greatly widened, and meanwhile, the special rheological property can reduce energy consumption in the material processing process.

In the above technical solution, the aliphatic copolyester is preferably polyethylene glycol succinate adipate (PESA), polypropylene glycol succinate adipate (PPSA), polybutylene succinate adipate (PBSA), polyethylene glycol succinate adipate (PHSA), or the like.

In the technical scheme, the blend material is most preferably 20 to 80 mass percent of cellulose acetate butyrate and 80 to 20 mass percent of polybutylene succinate adipate, the synergistic interaction of the cellulose acetate butyrate and the polybutylene succinate adipate is the best, and the rheological property and the compatibility of the obtained blend are both the best.

In the above technical solution, the number average molecular weight of the blend material is preferably at least greater than 20000g/mol, and more preferably at least greater than 40000 g/mol; the weight average molecular weight is preferably at least more than 60000g/mol, more preferably at least more than 80000 g/mol. .

In the above technical solution, the blend material preferably further contains at least one of a compatibilizer, an inorganic filler, an antioxidant, a lubricant, a colorant, and the like.

In the above solution, the melt viscosity of the blend is preferably at a low shear rate (100 s)^-1) Under the condition that the ratio of the mass of the copolyester to the mass of the thermoplastic cellulose is at least 50 percent lower than the blending addition theoretical value of the two starting materials (preferably, the mass ratio of the copolyester to the thermoplastic cellulose is 65 percent: 35 percent to 20 percent: 80 percent), and further preferably, the ratio of the mass ratio of the copolyester to the mass of the thermoplastic cellulose is at least 60 percent lower (preferably, the mass ratio of the copolyester to the mass of the thermoplastic cellulose is 50 percent: 50 percent to 35 percent: 65 percent).

In the above-mentioned embodiment, the melt viscosity of the blend is preferably at a high shear rate (1363 s)^-1) Under the condition that the ratio of the mass of the copolyester to the mass of the thermoplastic cellulose is at least 50 percent lower than the blending addition theoretical value of the two starting materials (preferably, the mass ratio of the copolyester to the thermoplastic cellulose is 65 percent: 35 percent to 20 percent: 80 percent), and further preferably, the ratio of the mass ratio of the copolyester to the mass of the thermoplastic cellulose is at least 70 percent lower (preferably, the mass ratio of the copolyester to the mass of the thermoplastic cellulose is 35 percent: 65 percent to 20 percent: 80 percent).

In the above technical solutions, the melt index of the blend material is preferably at least about 20% higher, more preferably at least about 100% higher (preferably 50% to 20% to 80% by mass ratio of the copolyester to the thermoplastic cellulose), and more preferably at least about 200% higher (more preferably 35% to 65% to 20% to 80% by mass ratio of the copolyester to the thermoplastic cellulose).

The aliphatic copolyester applied to the present invention can be prepared from various aliphatic diacids and aliphatic diols through polymerization. The catalyst for polymerization includes compounds containing metallic tin, antimony, titanium, etc. Aliphatic copolyesters include chain-extended aliphatic copolyesters, and various compounds or polymers reactive with carboxyl or hydroxyl groups can be used as chain extenders, including, for example, isocyanates containing two or more functional groups such as hexamethylene diisocyanate (HMDI). Suitable chain extenders include compounds containing multiple epoxy functional groups, such as those produced by BASF

ADR-4368C,

ADR-4368CS and the like. The chain extender of the present invention is present in an amount of from 0.2 to 4% by mass, and in some embodiments from 0.5 to 3% by mass.

The aliphatic copolyesters in the present invention include linear and branched copolyesters. The synthesis of branched copolyesters involves the addition of one or more branching agents during the synthesis. The branching agent is generally a polybasic acid having two or more carboxyl groups, a polyhydric alcohol or a polyhydroxy acid having two or more hydroxyl groups, or the like. Suitable branching agents include glycerol, trimethylolethane, trimethylolpropane, 1,2, 4-butanetriol, pentaerythritol, 1,2, 6-hexanetriol, sorbitol, 1,2, 3-benzenetricarboxylic acid (hemimellitic acid), 1,2, 4-benzenetricarboxylic acid (trimelitic acid), 1,3, 5-benzenetricarboxylic acid (trimesic acid), anhydrides, and the like.

In order to solve the second technical problem, the technical scheme adopted by the invention is as follows: the method for preparing the thermoplastic film of the blend of the thermoplastic cellulose and the aliphatic copolyester with the special rheological property adopts melt blending, uniformly mixes the required amount of the thermoplastic cellulose and the required amount of the aliphatic copolyester in a molten state, directly prepares a film from a blend melt, or prepares a film from the blend melt by cooling and granulating the blend melt and then melt extruding the blend particles.

In the above technical solution, the melt blending method of the blend of the thermoplastic cellulose and the aliphatic copolyester is preferably a twin-screw continuous extrusion method.

In the above technical scheme, the melt blending method of the blend of thermoplastic cellulose and aliphatic copolyester preferably comprises the steps of continuously extruding and granulating the thermoplastic cellulose powder, blending the thermoplastic cellulose powder and the aliphatic copolyester according to a required ratio, and then adding the mixture into a double-screw extruder for extrusion and granulation.

In the above technical scheme, the melt blending method of the blend of thermoplastic cellulose and aliphatic copolyester preferably comprises the steps of continuously extruding and granulating the thermoplastic cellulose powder, and then respectively metering the thermoplastic cellulose powder and the aliphatic copolyester into a twin-screw extruder according to the required feeding proportion to perform extrusion granulation.

In the above technical scheme, the melt blending method of the blend of thermoplastic cellulose and aliphatic copolyester preferably comprises the steps of respectively metering thermoplastic cellulose powder and aliphatic copolyester according to a certain feeding proportion into a twin-screw extruder for extrusion granulation.

In the above technical solution, the screw rotation speed of the melt blending method of the thermoplastic cellulose and aliphatic copolyester blend is preferably 50rpm to 1500rpm.

In the above technical solution, the temperature of the melt blending method of the thermoplastic cellulose and the aliphatic polyester blend is preferably 140 ℃ to 240 ℃.

In the above technical scheme, the method for directly making the blend melt into the film, preferably a twin-screw blending extrusion film-forming method, directly melts and mixes the required amount of the thermoplastic cellulose and the aliphatic copolyester in a twin-screw extruder, and then leads out the mixture through a casting film die or a blowing film die to make the film.

In the above technical scheme, the method for preparing the film from the blend particles by melt extrusion after cooling and granulating the blend melt is preferably a single-screw extrusion film-forming method, and the blend particles are melt extruded by a single-screw extruder and are led out by a casting film die or a blowing film die to prepare the film.

The materials and preparation methods used in the present invention are briefly described below:

1. thermoplastic cellulose

The thermoplastic cellulose is a cellulose derivative with a wide range, and the three hydroxyl groups on each repeated glucose unit of the cellulose derivative are partially or completely chemically modified in the forms of esterification or etherification and the like. The parameters characterizing the Degree of modification are the Degree of Substitution (Degree of Substitution), which is defined as the average number of substitutions in the three hydroxyl groups per repeating glucose unit, with a maximum of 3.0(3 hydroxyl groups are all substituted) and a minimum of 0 (pure cellulose).

The thermoplastic cellulose ester included in the present invention includes a mixed cellulose ester of cellulose and two or more kinds of organic aliphatic carboxylic acid, organic aliphatic acid anhydride and organic aliphatic acid halide, and the difference in the number of carbon atoms between different organic aliphatic carboxylic acid, organic aliphatic acid anhydride and organic aliphatic acid halide is 1 or more.

Cellulose esters are typically made by reacting natural cellulose with an organic acid, anhydride or acid chloride, etc., with a degree of substitution of the hydroxyl groups in the cellulose of from 0.5 to 2.8. Suitable cellulose ester products include Eastman, produced by Eastman chemical company, USA^TMCellulose acetate butyrate CAB-171-15, CAB-321-0.1, CAB-381-0.1, CAB-381-0.5, CAB-381-20, CAB-485-10, CAB-500-5, CAB-531-1 and the like. For example: CAB-531-1 contains 50% by mass of butyric acid component, 2.8% by mass of acetic acid component, and 1.7% by mass of hydroxyl component, and has a viscosity of 5.6 poise measured according to ASTM 1343. Cellulose esters are used in the fields of fibers, textiles, coatings, thermoplastic films, food additives, pharmaceutical industry and the like. In the coating industry, the addition of cellulose esters can improve the coating effect, including: hardness, flow, flatness, transparency, gloss, and the like. Cellulose Acetate Propionate (CAP) and Cellulose Acetate Butyrate (CAB) are two mixed cellulose esters that have a wide range of commercial uses.

2. Aliphatic copolyester

The aliphatic copolyester is a biodegradable plastic, and is prepared by condensation polymerization of at least two aliphatic diacids or aliphatic dianhydride, aliphatic diacid halide, aliphatic diacid ester and at least one aliphatic diol.

3. Blends of thermoplastic cellulose and biodegradable aliphatic copolyesters

The blend disclosed by the invention consists of thermoplastic cellulose and biodegradable aliphatic copolyester, wherein the mass content of the thermoplastic cellulose is 20-80%, and the mass content of the biodegradable aliphatic copolyester is 80-20%. The blend comprises, in addition to the above composition, at least one additive selected from the group consisting of: compatibility agents, inorganic fillers, antioxidants, lubricants, colorants, and the like.

The physical and chemical properties (such as melt viscosity, melt index, etc.) of the polymer blend are mainly determined by the types and composition ratios of the polymers constituting the polymer blend. The polymer type mainly determines the compatibility between the components of the blend, which is a measure of the interaction between different polymers, and when the interaction between different polymers is strong, it can be stably and uniformly mixed on a molecular scale, it is called a miscible (mismixing) system; the interaction between other polymers is weak, and the polymers can be stably and uniformly dispersed in a nano scale although the polymers cannot be mutually dissolved in a molecular scale, so that the blend is called a compatible system; other polymers have weak interactions and even if they are mixed by force, they tend to form separate phase regions, and such blends are incompatible systems. Polymer blend glass transition temperature (' T_g") information can be used as a simple judgment basis for the compatibility among the components [ multicomponent polymer-principle, structure and performance, King's institute and editions, 2013, p.20-22 ], if the blend respectively keeps the glass transition temperature of the raw material components, the compatibility among the components is not good, and if the blend only has one glass transition temperature, the compatibility among the components is better. Under the condition of determined polymer types, a certain functional relationship exists between some physical and chemical properties (such as melt viscosity, melt index and the like) of the blend and the composition ratio thereof [ handbook of plastics engineering handbook, Huangrui kingdom, 2000, p.633-637; melt Rheology of Polymer Blends from Melt Flow Index, International Journal of Polymeric Materials,1984,10, p.213-235, one can generally infer and even design Blends with specific properties. In some poorly compatible blending systems, a situation may occur in which the viscosity of the blend is lower than that of the raw material components [ fourth statistical mechanics, golden sun, 1998, p.630-633 ], the reason for this phenomenon being currently uncertain, one of which is explained by the interfacial slippage between the different phases leading to a decrease in the overall viscosity after mixing. Similar phenomena in compatibilityNo report is made on a good blend system, and the blend system has great potential if the phenomena can be applied to a system with good compatibility.

The theoretical properties of some polymer blends can be generally presumed by using the addition rule, and the addition theory can be expressed by the following formula:

P＝c₁P₁+c₂P₂

p is a property of the blend, c₁And P₁Is the concentration and nature of component 1; c. C₂And P₂Is the concentration and nature of component 2. The properties (P) of the blend of the thermoplastic cellulose and the aliphatic copolyester, such as melt apparent viscosity, melt index and the like, can be calculated by using an addition rule to obtain a theoretically predicted value, namely, the theoretically predicted value is defined as an addition theoretical value, and the value can be compared with the experimentally detected values, such as apparent viscosity, melt index and the like. The concentration of the components can be expressed by mass fraction or volume fraction, and the mass fraction is selected to calculate a theoretical value in the invention.

The blend of cellulose acetate butyrate ester and biodegradable polyester such as aliphatic copolyester, preferably polyethylene glycol succinate adipate (PESA), polypropylene glycol succinate adipate (PPSA), polybutylene succinate adipate (PBSA), polyethylene succinate adipate (PHSA) and the like, comprises 20-80% by mass of cellulose acetate butyrate ester and 80-20% by mass of aliphatic copolyester, and is characterized in that the melt viscosity of the blend is low shear rate (100 s)^-1) Under conditions at least 30% lower than the theoretical value of the mixed addition of the two starting materials. The melt viscosity of some more preferred compositions of the blends is at low shear rate (100 s)^-1) Under the condition, the addition ratio is at least 50 percent lower than the mixed addition theoretical value of the two starting materials; some of the most preferred compositions of the blends have melt viscosities at low shear rates (100 s)^-1) Under conditions at least 60% lower than the theoretical value of the mixed addition of the two starting materials.

A blend in accordance with one embodiment of the present invention comprises cellulose acetate butyrate ester and a biodegradable polyester such as an aliphatic copolyester, preferably polyethylene glycol succinate adipate(PESA), polytrimethylene adipate (PPSA), polybutylene succinate adipate (PBSA), polybutylene succinate adipate (PHSA), and the like, and the composition comprises 20 to 80 mass percent of cellulose acetate butyrate ester and 80 to 20 mass percent of aliphatic copolyester, and is characterized in that the melt viscosity of the blend is at a high shear rate (1363 s)^-1) Under conditions at least 30% lower than the theoretical value of the mixed addition of the two starting materials. The melt viscosity of some more preferred compositions of the blends is at high shear rate (1363 s)^-1) Under the condition, the addition ratio is at least 50 percent lower than the mixed addition theoretical value of the two starting materials; the melt viscosity of some of the most preferred compositions of the blends is at high shear rate (1363 s)^-1) Under conditions at least 70% lower than the theoretical value of the mixed addition of the two starting materials.

The blend specifically embodied by the invention comprises cellulose acetate butyrate ester and biodegradable polyester such as aliphatic copolyester, preferably polyethylene glycol succinate adipate (PESA), polypropylene glycol succinate adipate (PPSA), polybutylene succinate adipate (PBSA), polybutylene succinate adipate (PHSA) and the like, and comprises 20-80% by mass of cellulose acetate butyrate ester and 80-20% by mass of aliphatic copolyester, and is characterized in that the melt index of the blend is at least about 20% higher than the theoretical value of the mixed addition of the two starting materials. Some more preferred compositions have a melt index at least 100% higher than the theoretical value of the mixed addition of the two starting materials; some of the most preferred compositions of the blend have a melt index at least 200% greater than the theoretical value of the mixed addition of the two starting materials.

The invention relates to a method for preparing a blend of thermoplastic cellulose and aliphatic copolyester. The method comprises uniformly mixing thermoplastic cellulose 20-80 wt% and aliphatic copolyester 80-20 wt% in a continuous process, and extruding and granulating to obtain a blend with low shear rate (100 s)^-1) Under the condition, the additive ratio is at least 30 percent lower than the blending additive theoretical value of the two starting materials; at high shear rate (1363 s)^-1) Under conditions at least 30% lower than the theoretical value of the additive blend of the two starting materials, and the blendIs at least about 20% higher than the theoretical value of the additive blend of the two starting materials.

The blends of the present invention, which are proportioned "unusually" and "unexpectedly" have an apparent shear Viscosity lower than the theoretical value of the additive mixture of pure thermoplastic cellulose and aliphatic copolyester starting materials, i.e., exhibit a "concave" curve in the "apparent Viscosity-composition" relationship, which is reflected by the "Melt Viscosity trap" (Melt Viscosity Well) phenomenon, indicating that the blends have an "Anti-synergistic Effect" (either Effect or-synergistic Effect) of apparent Viscosity.

The blend of the present invention, which is composed in a certain proportion, has a Melt index (MFR: Melt Flow Rate) higher than the theoretical value of the mixed addition of pure thermoplastic cellulose and aliphatic copolyester starting material, i.e., in the relation of "Melt index-composition", it shows a "convex" curve, showing the phenomenon of "Melt index Peak" (MFR Peak), showing that the blend has a "Synergistic Effect" of Melt index (Synergistic Effect).

The blends of the invention have a number average molecular weight of at least more than 20000g/mol and a weight average molecular weight of at least more than 60000 g/mol. The blends of the invention preferably have a number average molecular weight of at least greater than 40000g/mol and a weight average molecular weight of at least greater than 80000 g/mol.

4. Method for producing blends of thermoplastic cellulose and biodegradable aliphatic copolyesters

The continuous melting preparation method comprises a two-step method and a one-step method. In the two-step method, thermoplastic cellulose powder is firstly granulated by a single-screw or double-screw extruder, then thermoplastic cellulose particles and aliphatic copolyester particles are uniformly mixed according to a certain proportion, and then the particle blend is added into a feeding port of the double-screw extruder by a feeding machine according to a certain feeding rate. The feeder can be a weight loss feeder or a volume feeder. The other embodiment is that two feeders are adopted to respectively meter the thermoplastic cellulose particles and the aliphatic copolyester particles into a double-screw extruder according to a certain feeding proportion for extrusion granulation.

The one-step method of the invention is that the thermoplastic cellulose powder is directly added into the feeding port of the double-screw extruder by one feeder according to a certain feeding rate without being processed and granulated by heat, meanwhile, the aliphatic copolyester particles are added into the feeding port of the double-screw extruder by the other feeder according to a certain feeding rate, the double-screw extrusion is carried out, and the extruded sample strips are granulated by a water tank or underwater to prepare the blend particles. The extrudate can also be air cooled by an anhydrous process and then pelletized.

Extrusion temperatures suitable for the present invention are preferably from 140 ℃ to the lower thermal decomposition temperatures of the thermoplastic cellulose and aliphatic copolyester, more preferably from 140 ℃ to 240 ℃. The rotation speed of the extruder is preferably 50rpm to 1500rpm, more preferably 100rpm to 800 rpm.

Melt blending devices suitable for use in the present invention include a variety of mixers, Farrel continuous mixers, Banbury mixers, single screw extruders, twin screw extruders, multiple screw extruders (more than two screws), reciprocating single screw extruders such as Buss reciprocating single screw extruders (Buss Ko-Kneader), and the like. Preferred processes are continuous melt blending extrusion processes including twin screw extrusion processes. Continuous twin-screw extruders suitable for use in the present invention include twin-screw extruders of different designs, such as the ZSK Mcc18 co-rotating parallel twin-screw extruder manufactured by Coperion, Germany, and the like.

The present invention demonstrates that the thermoplastic cellulose prepared by the twin screw continuous melt coextrusion process has an "unexpected" low melt viscosity when blended with an aliphatic copolyester. One embodiment of the invention is that under the same conditions, the melt viscosity of the blend is lower than the theoretical value of the mixed addition of the thermoplastic cellulose and the aliphatic copolyester starting materials. This viscosity reduction is prevalent, including at lower shear rates such as 100s^-1And at higher shear rates, e.g. 1363s^-1. At 100s^-1The melt viscosity of the blend is at least 30% lower than the theoretical value of the mixed addition of the two starting materials at shear rate. Some more preferred compositions (mass ratio of copolyester to thermoplastic cellulose 65%: 35% to 20%: 80%) of the blends have a melt viscosityThe melt viscosity of the blend, which is at least 50% lower than the theoretical value of the mixed addition of the two starting materials, and some of the most preferred compositions (50%: 50% to 35%: 65% by mass of copolyester to thermoplastic cellulose) is at least 60% lower than the theoretical value of the mixed addition of the two starting materials. At 1363s^-1The melt viscosity of the blend at shear rate is at least 30% lower than the theoretical value of the mixed addition of the two starting materials, some more preferred compositions (65% by mass copolyester to thermoplastic cellulose: 35% to 20% to 80%) of the blend have a melt viscosity at least 50% lower than the theoretical value of the mixed addition of the two starting materials, and some most preferred compositions (35% by mass copolyester to thermoplastic cellulose: 65% to 20% to 80%) of the blend have a melt viscosity at least 70% lower than the theoretical value of the mixed addition of the two starting materials.

One concrete embodiment of the thermoplastic cellulose and aliphatic copolyester blend material prepared by the invention is that the melt index of the blend is higher than the mixing addition theoretical value of two starting materials. The melt index of the blend of preferred composition is at least about 20% higher than the theoretical value of the mixed addition of the two starting materials, more preferably the melt index of the blend of composition (50%: 50% to 20%: 80% by mass of copolyester to thermoplastic cellulose) is at least 100% higher than the theoretical value of the mixed addition of the two starting materials, and most preferably the melt index of the blend of composition (35%: 65% to 20%: 80% by mass of copolyester to thermoplastic cellulose) can be at least 200% higher than the theoretical value of the mixed addition of the two starting materials.

5. Method for preparing thermoplastic cellulose and biodegradable aliphatic copolyester blend film

The invention discloses a method for preparing a thermoplastic film of a blend of thermoplastic cellulose and aliphatic copolyester with special rheological properties, which is characterized in that the blend consists of 20 to 80 mass percent of thermoplastic cellulose and 80 to 20 mass percent of aliphatic copolyester. The blend was prepared by the continuous melt extrusion blending process described above. The melt viscosity of the blend was at a low shear rate (100 s)^-1) At least 30% lower than the theoretical value of addition under the condition; at high shear rate (1363 s)^-1) Specific addition under the conditionThe theoretical value is at least 30% lower and the melt index of the blend is at least about 20% higher than the theoretical value of the blended addition of the two starting materials. The blend thermoplastic film of the invention has a Young's modulus of greater than 220MPa, a breaking strength of greater than 10MPa, and an elongation at break of greater than 60%. In the method, the blend is melted and extruded in a screw extruder, the blend melt passes through a die, and the oriented stretching is further controlled to obtain a film with certain thickness.

The invention discloses a method for preparing a thermoplastic film of a blend of thermoplastic cellulose and aliphatic copolyester with special rheological property, which is a single-screw extrusion film-forming method. In the method, a blend prepared in advance is added into a single-screw extruder, the single-screw extruder is generally divided into three stages on the effective length, the first stage is a conveying section, and the blend is preheated and extruded at the first stage; the second section is a compression section, the depth of the thread groove is greatly reduced, and the melt temperature reaches the degree of plasticizing and melting the blend; the third section is a metering section, and the blend melt is conveyed to a film die according to a certain melt flow rate under the rotation of a screw.

One film forming method of the present invention is a cast film forming method. And cooling the cast film by a multistage cooling roller to obtain the solidified cast film. The thickness of the casting film is controlled by the melt extrusion speed and the rotation speed of the winding roller, and the orientation degree of the casting film can be further controlled by the above parameters. The cast film has a high degree of molecular orientation in the longitudinal or Machine Direction (MD) of the film, and therefore the cast film has a high tensile strength and young's modulus in this direction, but as the degree of orientation increases, the elongation of the film in the longitudinal direction decreases accordingly. The Direction perpendicular to the machine Direction is the Transverse Direction (CD), the cast film has substantially no orientation in the Transverse Direction, and the properties of the cast film in both the MD and CD directions generally differ greatly due to the difference in the degree of orientation.

In the film blowing processing method, the blend melt is extruded out of a hollow film bubble which is nearly cylindrical through a circular ring-shaped opening die, the film bubble is a sealing system which is filled with gas with certain pressure in advance, and the top end of the film bubble is provided with a press roll. The double-layer film on the top is drawn by a series of rollers and then cut and respectively rolled. The thickness of the film is determined by a series of conditions including the rotation speed of the extruder, the take-up speed of the film, and the like. Films produced by blown film processes are more nearly performance in both the machine and transverse directions than cast films because of their orientation.

The extrusion temperature of the blend thermoplastic film is from 140 ℃ to 240 ℃, preferably from 160 ℃ to 220 ℃. The number of revolutions of the single-screw extruder is 10 to 500rpm, preferably 20 to 300 rpm.

The invention relates to a method for preparing a thermoplastic film, in particular to a double-screw extrusion film-forming method. The process is different from the single screw extruder method, the feeding rate of the blend is completed by one feeder, the feeder suitable for the invention comprises a weight loss type feeder or a volume type feeder, the tail end of the double screw extruder is provided with a cast film die or a blown film die, and the film led out from the die is further formed.

The other method of the invention is a method for directly blending twin-screw to form film by one-step method, on a twin-screw extruder provided with a casting film die or a blowing film die, thermoplastic cellulose powder or granules and aliphatic copolyester are added into a feeding area of the twin-screw extruder according to a certain mass proportion, and the blended melt after plasticizing, melting and blending enters a melt metering pump, wherein the metering pump can be a gear pump and has the functions of accurately controlling the flow rate of the melt and directly adding the blended melt into the casting film die or the blowing film die at a certain stable flow rate to extrude the film. The process has the advantages that a granulation process is not needed, the energy consumption can be effectively reduced, the whole process is more green, low-carbon and environment-friendly, and the preparation cost of the film is also effectively reduced.

The Young's modulus of the prepared film blend thermoplastic film is related to the stiffness or stiffness of the film. When the Young's modulus of the film is high, the film has high rigidity and stiffness, and the film material is not easily subjected to tensile deformation. Conversely, the Young's modulus of the film is small, and the rigidity or stiffness thereof is also low. The elongation at break of a film material is related to the ductility and toughness of the material, and the higher the elongation at break, the greater the deformation that the material can undergo during processing and the better the toughness. The larger the breaking strength is, the better the bearing performance of the film is.

The thermoplastic film has Young modulus of more than 220MPa, breaking strength of more than 10MPa and elongation at break of more than 60 percent. The preferred thermoplastic films of the present invention (preferred copolyester to thermoplastic cellulose mass ratio 50%: 50%) have a Young's modulus greater than 500MPa, a breaking strength greater than 30MPa, and an elongation at break greater than 150%. (is there a better film, the composition of which can be summarized

The thermoplastic film of the blend of the thermoplastic cellulose and the aliphatic copolyester prepared by the continuous extrusion blending method disclosed by the invention has lower melt viscosity and higher melt index than the theoretical value of the mixing addition of two pure raw materials, the film utilizes the synergistic performance advantage of the two raw materials, the Young modulus is greater than 220MPa, the breaking strength is greater than 10MPa, and the breaking elongation is greater than 60%, so that better technical effects are achieved.

Drawings

FIG. 1180 ℃ is a plot of apparent shear viscosity versus shear rate for each PBSA/CAB particle.

FIG. 2180 ℃ for each PBSA/CAB particle at 100s^-1The dashed line in the figure is a line of addition theory calculated values for the relationship between apparent shear viscosity and composition at shear rate of (2).

FIG. 3180 ℃ for each PBSA/CAB particle at 1363s^-1The dashed line in the figure is a line of addition theory calculated values for the relationship between apparent shear viscosity and composition at shear rate of (2).

FIG. 4 DSC cooling curves for each PBSA/CAB particle.

FIG. 5 DSC second temperature rise profile for each PBSA/CAB particle.

FIG. 6 is a graph showing the relationship between the glass transition temperature and the composition of each PBSA/CAB particle.

FIG. 7 TGA curves of PBSA/CAB particles in air atmosphere.

FIG. 8 is a graph showing the relationship between the melt index (190 ℃,2.16kg) and the composition of each PBSA/CAB particle, wherein the dotted line represents a line of addition theoretical calculation values.

FIG. 9 shows the relationship between the elongation at break and the composition of each PBSA/CAB film.

FIG. 10 shows the relationship between the breaking strength and the composition of each PBSA/CAB film.

FIG. 11 modulus vs. composition for each PBSA/CAB film.

FIG. 12 correlation of fracture energy and composition for each PBSA/CAB film.

FIG. 13 DSC cooling curves for each PLA/CAB particle.

FIG. 14 DSC second temperature rise profile for each PLA/CAB particle.

FIG. 15 the relationship between melt index (190 ℃,2.16kg) and composition for each PLA/CAB particle.

Graph apparent shear viscosity versus shear rate for each PLA/CAB particle at 16200 ℃.

Graph 17200 deg.C for each PLA/CAB particle at 100s^-1The apparent shear viscosity versus composition at shear rate of (3).

At 18200 ℃ for each PLA/CAB particle at 1363s^-1The apparent shear viscosity versus composition at shear rate of (3).

FIG. 19 DSC cooling curves for each PBS/CAP particle.

FIG. 20 DSC second temperature rise profile for each PBS/CAP particle.

The invention carries out performance measurement according to the following method:

melt index (MFR) determination method: according to ISO 1133 standard, Lloyd DAVENPORT is adopted^TMThe melt index was measured by an MFI-10/230 melt index meter, the cylinder temperature was 190 ℃, the weight load was 2.16kg, the diameter of the die was 2.095mm, the length was 8mm, the preheating time was 4min, samples were automatically cut at set intervals, 5 times of averaging was performed, and the measurement result was expressed in grams per 10 minutes (g/10 min).

Rheological behavior determination method: measured by a Malvern Instruments Rosand RH7 hot high pressure capillary rheometer with the processing software of Lannch

Version 8.60. Selection of testA sensor with a pressure of 10000Psi and a capillary die of a round hole type of 16/1.0/180. For batch loading compaction at the time of loading, two 0.5MPa preloads and 2 minute preheats were performed prior to testing to ensure complete melting and compaction of the particles at the selected temperature (180 ℃). The test was chosen to determine the apparent shear viscosity at the following shear rates: 100,192,369,709,1363,2615, and 5019s^-1。

Thermogravimetric analysis (TGA): the testing was performed on a Discovery series thermogravimetric analyzer from TA Instruments with the processing software TA Instruments Trios version 3.1.4. The temperature of the isobalance chamber was required to be stabilized at 40 ℃ before testing. During testing, 5-10 mg of sample is weighed and placed in a ceramic crucible, and the test is carried out in the air atmosphere with the flow rate of 20mL/min, the temperature rise range is 30-600 ℃, and the temperature rise rate is 10 ℃/min.

Thermal performance analysis (DSC): the tests were performed on a Discovery series Differential Scanning Calorimeter (DSC) manufactured by TA Instruments, Inc., with the processing software TA Instruments Trios version 3.1.5, equipped with a calibrated Cooling System 90 mechanical refrigeration accessory. The testing atmosphere is 50mL/min of nitrogen, and the amount of the sample required by the test is 5-10 mg. The test procedure was as follows: the temperature is stabilized at 40 ℃, then the temperature is raised to 250 ℃ at the speed of 10 ℃/min and the temperature is kept constant for 2min to remove the thermal history, then the temperature is lowered to-70 ℃ at the speed of 10 ℃/min, and then the temperature is raised to 250 ℃ at the speed of 10 ℃. And recording the temperature reduction process and the second temperature rise process to research the thermal performance of the sample. By DSC measurement, software can be used to directly derive the crystallization temperature ("T") of a sample_c"), melting temperature (" T ")_m"), glass transition (" T ")_g"), enthalpy change (" △ H "), etc.

Film tensile test: the measurement was carried out according to ISO 527-3 using a model 3344 materials tester from INSTRON with the processing software Bluehill version 2.31. The film was cut into Type 5 according to ISO 527-3, and placed in a Bluepard BPS-100CB constant temperature and humidity cabinet (temperature 23 ℃ C., relative humidity 50%) of Shanghai-Hengchan scientific instruments Co., Ltd. for 24 hours. During testing, the initial clamp spacing was 75mm, the test pull rate was 100mm/min, and each sample was tested 5 times, and the average value was taken.

Detailed Description

The present invention is specifically described by the following examples. It should be noted that the following examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, as many insubstantial modifications and variations of the invention may be made by those skilled in the art in light of the above teachings.

Comparative example 1

The polybutylene succinate adipate (PBSA) used in the invention is produced by Showa Denko K.K. under the brand number

MD 3001. Raw materials

MD3001PBSA particles from PolyLab HAAKE, Thermo Fisher technologies, USA^TMRheomex OS PTW16 was pelletized by extrusion from a co-rotating twin-screw extruder (screw diameter 16mm, L/D. 40) as a comparative example. The extruder has a total of 11 sections from the feed port to the die, numbered 1-11, wherein section 1 serves only as a feed and is not heated. A volume type particle feeder attached to the extruder and used for feeding the particles after calibration

MD3001PBSA raw material was fed to twin screw at a feed rate of 2100 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 53-55%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The melt index of the particles at 190 ℃ under 2.16kg was 2.39g/10 min.

Comparative example 2

Cellulose Acetate Butyrate (CAB) used in the present invention was obtained from Eastman, USA^TMCompany, brand Eastman^TMCAB-381-0.5. Raw material Eastman^TMCAB-381-0.5 powder, PolyLab HAAKE from Thermo Fisher scientific, USA^TMRheomex OS PTW16 was pelletized by extrusion from a co-rotating twin-screw extruder (screw diameter 16mm, L/D. 40) as a comparative example. The extruder has a total of 11 sections from the feed port to the die, numbered 1-11, wherein section 1 serves only as a feed and is not heated. The attached volumetric powder feeder of the extruder is used for Eastman after being calibrated^TMCAB-381-0.5 raw material is fed into the twin screw, and the feeding speed is 940 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 55-57%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The melt index of the particles at 190 ℃ under 2.16kg was 5.60g/10 min.

[ example 1 ]

MD3001PBSA and Eastman^TMCAB-381-0.5 PolyLab HAAKE as mentioned hereinabove^TMMelt blending and extruding in a Rheomex OS PTW16 co-rotating twin-screw extruder for granulation. In section 1 of the extruder, a calibrated volumetric particle feeder was used

Feeding of MD3001PBSA particles at the speed of: 1680g/hr, while a calibrated volumetric powder feeder was used in Eastman^TMFeeding CAB-381-0.5 powder at the speed of: 420 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 48-52%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The granules are at 190 deg.C and 2.16kgHas a melt index of 3.73g/10 min.

[ example 2 ]

Feeding of MD3001PBSA particles at the speed of: 1365g/hr, while calibrated volumetric powder feeder is used for Eastman^TMFeeding CAB-381-0.5 powder at the speed of: 735 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 43-47%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The melt index of the particles at 190 ℃ under 2.16kg was 5.96g/10 min.

[ example 3 ]

Feeding of MD3001PBSA particles at the speed of: 1050g/hr, while a calibrated volumetric powder feeder is used for Eastman^TMFeeding CAB-381-0.5 powder at the speed of: 1050 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 deg.C, 150 deg.C, 160 deg.C160 ℃,160 ℃,160 ℃ and 160 ℃, the screw speed is set at 200rpm, and the torque is between 41 and 43 percent. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The pellets had a melt index of 9.95g/10min at 190 ℃ under 2.16 kg.

[ example 4 ]

Feeding of MD3001PBSA particles at the speed of: 735g/hr, while a calibrated volumetric powder feeder is used in Eastman^TMFeeding CAB-381-0.5 powder at the speed of: 1365 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 42-44%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The melt index of the particles at 190 ℃ under 2.16kg was 14.69g/10 min.

[ example 5 ]

Feeding of MD3001PBSA particles at the speed of: 420g/hr, while the calibrated volumetric powder feeder is used in Eastman^TMFeeding CAB-381-0.5 powder at the speed of: 1680 g/hr. The temperatures of 2-11 sections of the extruder are respectively as follows: 140 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 48-52%. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. Collecting particles, vacuum drying at 60 deg.C for 4hr, and packaging. The melt index of the particles at 190 ℃ under 2.16kg was 14.98g/10 min.

[ example 6 ]

All 7 of the above particles, including comparative examples 1-2 and examples 1-5, were subjected to rheological behavior measurements on a Malvern instruments and RH7 hot high pressure capillary rheometer, the test method being as described above. The apparent shear viscosity of each particle at 180 ℃ is related to the shear rate in FIG. 1. Wherein the shear rate is 100s^-1And 1363s^-1The apparent shear viscosity versus composition is shown in FIGS. 2 and 3, respectively, with specific values listed in tables 1 and 2.

From FIG. 1, it can be seen that the shear thinning phenomenon, i.e., the shear viscosity decreases with increasing shear rate, is very common in polymer systems, indicating that the basic properties of the system do not change significantly after blending. And in most cases the apparent shear viscosity of the mixture is below that of the two pure materials under the same conditions, i.e., the viscosity of the two materials decreases after mixing. Referring specifically to fig. 2 and 3, it has been found that the apparent shear viscosity of the blended particles is lower than that of either pure starting material, and the viscosity curve is "concave," an unexpected phenomenon of "viscosity trapping," which indicates that the blended particles become less viscous at both high and low shear rates, a property that is rarely encountered in compatible polymer blends.

Some performance parameters after blending of the polymer can be presumed by addition theoretical values, and are determined according to the following formula:

P＝c₁P₁+c₂P₂

wherein P is the theoretical value of addition, P₁The corresponding parameter values for component 1 in the mixture, c₁Is its mass fraction, P₂The corresponding parameter value of component 2 in the mixture, c₂Is the mass fraction thereof. If the measured value of the mixture parameter differs more from the theoretical value of the addition, a more pronounced synergistic (or anti-synergistic) action between the components is indicated.

From Table 1, it can be found that when the shear rate is 100s^-1When the actual blend apparent shear viscosity is about 31.6% (example 1) to 60.6% (example 4) lower than the addition theoretical value.

From Table 2, it can be found that when the shear rate is 1363s^-1When the actual blend apparent shear viscosity is about 33.7% (example 1) to 69.4% (example 5) lower than the addition theoretical value.

[ example 7 ]

All of the above 7 particles, including comparative examples 1-2 and examples 1-5, were subjected to Differential Scanning Calorimetry (DSC) tests according to the procedure described above, and the cooling curve and second heating curve are shown in fig. 2. The crystallization temperature ("T") can be directly derived therefrom by software_c"), melting temperature (" T ")_m"), glass transition (" T ")_g"), enthalpy change (" △ H "), and the like, and specific values are shown in Table 2_g") versus composition is shown in fig. 3.

It can be seen from fig. 2 that the crystallinity of PBSA is significantly reduced after adding CAB, the particles of examples 1-5 have no crystallization peak during the temperature reduction process, only the second temperature rise curve of example 1 has a crystallization peak, but the crystallization temperature and the peak area are both smaller than those of pure PBSA particles, and the corresponding melting peak temperature and area are also smaller than those of pure PBSA particles (see table 2 for detailed data). All particles have only one glass transition temperature ("T_g") indicates that the compatibility of the components in the blended particles is good, and T_gThe values of (a) increase with increasing CAB content, see fig. 3.

[ example 8 ]

All 7 of the above particles, including comparative examples 1-2 and examples 1-5, were subjected to thermogravimetric analysis (TGA) testing according to the procedure described above, and the results of the testing are shown in fig. 4. It can be seen from the figure that the thermal decomposition curves of the particles after blending are substantially between the curves of the two comparative examples, indicating that the thermal decomposability of CAB and PBSA did not change much before and after blending, which is in agreement with the expectation.

[ example 9 ]

All of the above 7 types of particles, including comparative examples 1-2 and examples 1-5, were subjected to melt index (MFR) testing (190 ℃,2.16kg) according to the procedure described above, and the relationship between the measured MFR values and the composition is shown in FIG. 5. The specific values obtained from FIG. 5 are listed in Table 4, which includes the "theoretical values for addition" mentioned above.

From Table 4, it can be seen that the actual melt index of example 1 is 0.70g/10min higher than the theoretical value of addition after melt blending PBSA and CAB, the percentage being about 23.0%; the actual melt index of example 4 was 10.21g/10min higher than the theoretical value of addition, the percentage was about 228%, and the percentage value in the examples was the largest. All of these exceptionally high melt indices are unexpected, rare in compatible polymer blend systems, and not yet discovered in CAB and PBSA blends.

[ example 10 ]

All 7 of the above particles, including comparative examples 1-2 and examples 1-5, HAAKE manufactured by Thermo Fisher scientific Inc. of U.S.A^TMCast films were prepared on a Rheomex OS single screw extruder having a screw diameter of 19mm and a length to diameter ratio of 25 equipped with a 3:1 standard metering screw, made from HAAKE^TMPolyLab^TMOS torque rheometer platform control. The extruder has three heating sections, the numbers of the heating sections from a feed inlet to an outlet are respectively 1-3, a casting die with the width of 150mm and the opening height of 0.6mm is configured, and a film is prepared by the drawing and stretching of three subsequent guide rollers at 40 ℃. The thickness of the casting film is controlled to be 30 to 50 μm by adjusting the rotation speed of the guide roll. The production conditions of all 7 kinds of cast films are shown in Table 5.

The films were subjected to the film tensile test described above and the results of the Machine Direction (MD) tensile test are shown in Table 6. The poly (butylene succinate-co-adipate) (PBSA) cast film (comparative example 1) has a lower modulus (277MPa), is a softer low-stiffness, low-stiffness film, has an elongation of up to 336% and a strength of 36.1 MPa. The Cellulose Acetate Butyrate (CAB) cast film (comparative example 2) has a high modulus (1181MPa), is a high-stiffness or high-rigidity film, but has a very low elongation (7.6%) which is only about 2% of that of a PBSA film, is a very brittle film, and is easy to break in the processing application range due to low toughness, so that the industrial application range is limited.

By using the method for preparing the blend with special rheological property disclosed by the invention, a series of novel PBSA/CAB blend films with moderate tensile property are obtained. Fig. 9 shows that the elongation at break of the films of examples 1 to 5 is higher than that of the CAB film, and that these films have a wider range of applications than the CAB film due to the improvement in ductility. Particularly prominent are the higher elongation at break of the films of examples 1 and 2, 136% and 195% higher than pure PBSA, respectively, indicating a clear "synergistic effect" between PBSA and CAB.

The fracture strength of these films was between 11MPa and 35MPa, as shown by the properties of the films prepared in examples 1 to 5 in fig. 10. The modulus of the film is between 227MPa and 1094MPa (see figure 11), and the fracture energy of the film is 15.6MJ/m³To 107.2MJ/m³Wherein the fracture energy of example 1 and example 2 is "unusual" higher than the higher of the two starting material films (PBSA films), both at 107.2MJ/m (see FIG. 12)³On the other hand, about 30% higher than the PBSA film, indicating that both films have better toughness than the starting material. These experimental results show that the combination of tensile properties of the film prepared by the present invention is not possessed by the film prepared by the starting materials PBSA and CAB, so that the present invention widens the application field and range of the raw film.

Comparative example 3

Adopts aliphatic polyester-polylactic acid (Nature Works Ingeo)^TM4032D) With thermoplastic cellulose CAB (Eastman)^TMCAB-381-0.5) The same processing method is adopted for melt blending extrusion, and PLA is non-polyester aliphatic copolyester. The mixing proportion is selected as PLA/CAB (mass ratio): 0/100,20/80,35/65,50/50,65/35,80/20, and 100/0. Mixing was also carried out in PolyLab HAAKE^TMRheomex OS PTW16 co-rotating twin screw extruder, and simultaneously adding Ingeo to the 1 st section of the extruder in proportion by using a volumetric feeder of the extruder^TM4032D PLA and Eastman^TMCAB-381-0.5. The temperatures of 2-11 sections of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 200 ℃, and the screw rotation speed is set at 200 rpm. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. The particles were collected, evacuated in a vacuum oven at 60 ℃ for 4 hours, and then packaged for use.

The above seven dried PLA/CAB particles were subjected to Differential Scanning Calorimetry (DSC) tests according to the above procedure, and the temperature decrease curves and the second temperature increase curves are shown in fig. 13 and 14. It is evident from FIGS. 13 and 14 that there are two glass transition temperatures ("T" s) in the PLA/CAB blend particles_g"), at about 60 ℃ and 115 ℃ respectively, with pure Ingeo^TM4032DPLA and Eastman^TMCAB-381-0.5 agreement, which indicates that Ingeo^TM4032D PLA and Eastman^TMCAB-381-0.5 is not good in compatibility, phase separation exists after blending, and it can be seen from FIG. 4 to FIG. 6

MD3001PBSA and Eastman^TMCAB-381-0.5 blend only has one glass transition temperature ("T_g") that is

MD3001PBSA and Eastman^TMThe compatibility of CAB-381-0.5 is good.

The above seven dried PLA/CAB particles were measured for melt index (MFR) at 190 deg.C, 2.16kg as described above, and the results are shown in FIG. 15; in addition, each PLA/CAB particle was measured for capillary rheology at 200 ℃ as described aboveProperties, test results are shown in FIG. 16, low shear rate (100 s)^-1) And high shear rate (1363 s)^-1) The apparent viscosity versus composition of the resulting polymer is shown in FIGS. 17 and 18, respectively. From FIG. 15, it can be seen that the melt indexes of the mixed particles are basically around the theoretical value of the mixing addition, and conform to the mixing addition law; and it can be found from fig. 16 that the viscosity curve of most mixed particles is between two pure raw materials, and although there are cases in fig. 17 and fig. 18 where the viscosity of the blend is less than the theoretical value of the mixed addition in a narrow range, it is difficult for the PLA/CAB blended particles to satisfy both the "viscosity trap" and "melt index peak" phenomena. This again demonstrates that the thermoplastic cellulose and aliphatic copolyester blends with specific rheological properties disclosed in the present invention achieve an "unexpected" technical effect.

Comparative example 4

Aliphatic polyester polybutylene succinate (PBS) (showa electrical,

MD 3001) and thermoplastic cellulose CAP (Eastman)^TMCAP-375E 4000012) was melt blended and extruded using the same processing method, CAP was not suitable for the thermoplastic cellulose types disclosed in this invention. The mixing ratio is selected as PBS/CAP (mass ratio): 0/100,20/80,40/60, 50/50, 60/40,80/20, and 100/0. Mixing was also carried out in PolyLab HAAKE^TMRheomex OSPTW16 co-rotating twin screw extruder, and proportionally adding into the 1 st section of the extruder simultaneously by using a volumetric feeder of the extruder

MD3001PBS and Eastman^TMCAP-375E 4000012. The temperatures of 2-11 sections of the extruder are respectively as follows: 160 ℃,170 ℃,180 ℃,180 ℃,180 ℃,180 ℃,180 ℃,180 ℃ and 180 ℃, the screw speed being set at 200 rpm. The extruder is provided with a circular neck ring die with the diameter of 3mm, and a sample strip is extruded from the neck ring die, cooled in water bath and cut into cylindrical particles with the diameter of about 3mm by a granulator. The particles were collected, evacuated in a vacuum oven at 60 ℃ for 4 hours, and then packaged for use.

The above seven kindsPBS/CAP particles, DSC measurements were performed as described above, and the cooling and second heating curves are shown in FIGS. 19 and 20, respectively. It is apparent from fig. 19 and 20 that the crystallization and melting processes of both PBS and CAP remain after mixing, except that the crystallization temperature of PBS is raised from about 80 ℃ for pure materials to about 90 ℃ after blending, while the crystallization temperature of CAP is maintained substantially at about 78 ℃; the melting temperatures before and after blending of PBS and CAP were substantially unchanged, being about 114 ℃ and 93 ℃ respectively. Although no significant glass transition temperature (T) of CAP was seen_g) T before and after PBS mixing_gThe data above, which are always maintained at about-30 c, show poor compatibility of PBS and CAP in the blend, phase separation of the two, and crystallization essentially in the respective phase zones. As can be seen from FIGS. 4 to 6, there is only one T after blending PBSA and CAB_gAnd the crystallization process is also changed remarkably, namely the compatibility of the PBSA and the CAB is good.

The effect difference of the comparative examples 3 and 4 and the examples 1 to 5 means that the different types of the blends of different aliphatic copolyesters and thermoplastic cellulose are very different, such as between PLA, PBS and PBSA, and between CAB and CAP, although the materials are commonly used in the field, the properties of the blended blends are very different due to the difference of the performances, and the effect cannot be expected. Moreover, the application range of the starting raw materials can be widened, and the energy consumption in the material processing process can be reduced.

[ example 11 ]

The PLA/CAB blend particles were also subjected to a cast film preparation experiment under the conditions described in example 10, and it was found that the film was easily torn during the draw-stretch process due to its low melt strength, and thus it was difficult to obtain a thin and uniform cast film. This shows that the thermoplastic cellulose and aliphatic copolyester blend with special rheological behavior represented by PBSA/CAB disclosed by the invention has excellent performance and application potential in the field of films.

TABLE 1180 ℃ shear rate of 100s^-1The measured apparent shear viscosity, the theoretical shear viscosity, and the difference and the percentage difference between the two

TABLE 2180 ℃ measured apparent shear viscosity at a shear rate of 1363s-1, theoretical apparent shear viscosity, and difference and percent difference between the two

Table 3 thermal performance parameters of each particle obtained from DSC results.

From the second temperature rise curve.

Table 4 measured melt index (190 ℃,2.16kg) and addition theoretical melt index and the difference and percent difference between the two

TABLE 5 processing conditions for preparation of cast films

TABLE 6 tensile Properties (MD) of the PBSA/CAB cast films

Claims

1. A thermoplastic film of a blend of thermoplastic cellulose and an aliphatic copolyester, the blend comprising from 20% to 80%Blend of a mass of thermoplastic cellulose with 80 to 20 mass% of an aliphatic copolyester, characterized in that the melt viscosity of the blend is 100s at a low shear rate of 180 DEG C^-1Under the condition, the additive ratio is at least 30 percent lower than the blending additive theoretical value of the two starting materials; 1363s at high shear rate of 180 deg.C^-1Under the condition, the addition ratio is at least 30 percent lower than the blending addition theoretical value of the two raw materials; wherein the thermoplastic cellulose is cellulose acetate butyrate; the aliphatic copolymer is poly butylene succinate adipate.

2. The thermoplastic cellulose and aliphatic copolyester blend thermoplastic film according to claim 1, wherein the substitution degree of the thermoplastic cellulose is more than 1.0.

3. The thermoplastic film of a blend of thermoplastic cellulose and an aliphatic copolyester according to claim 1, wherein the blend has a number average molecular weight of at least 20000g/mol and a weight average molecular weight of at least 60000 g/mol.

4. A method for preparing the thermoplastic film of the blend of the thermoplastic cellulose and the aliphatic copolyester as claimed in any one of claims 1 to 3, characterized in that continuous melt blending extrusion is adopted, the required amount of the thermoplastic cellulose and the required amount of the aliphatic copolyester are uniformly mixed in a molten state, and extrusion granulation is carried out to obtain blend particles; the blend particles are melted and extruded in a screw extruder, the blend melt is extruded by a die, and the film is obtained by further controlled orientation and stretching.

5. A method for preparing the thermoplastic cellulose and aliphatic copolyester blend thermoplastic film according to any one of claims 1 to 3, characterized by adopting continuous melt blending extrusion, uniformly mixing the required amount of thermoplastic cellulose and the required amount of aliphatic copolyester in a molten state, extruding to obtain a melt blend, adding the melt blend into a die through a melt metering pump, and further controlling orientation and stretching to obtain the film.