CN107793709B

CN107793709B - Thermoplastic cellulose and aliphatic copolyester blend injection molding product and preparation method thereof

Info

Publication number: CN107793709B
Application number: CN201610805753.9A
Authority: CN
Inventors: 詹姆斯·洪学·王; 周炳
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: 2021-02-09
Anticipated expiration: 2036-09-06
Also published as: CN107793709A

Abstract

The invention relates to a blend injection molding product of thermoplastic cellulose and aliphatic copolyester, which mainly solves the technical problems that the application field of the thermoplastic cellulose is limited due to high viscosity and poor injection molding processability 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 at least about 30 percent lower than the blending addition theoretical value of two starting materials under the condition of low shear rate; the technical proposal that the theoretical value of blending addition of the two starting materials is at least 30 percent lower under the condition of high shear rate better solves the problem, and can be used in the industrial production of thermoplastic cellulose and aliphatic copolyester injection molding products.

Description

Thermoplastic cellulose and aliphatic copolyester blend injection molding product 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 injection product of thermoplastic cellulose and aliphatic copolyester with special rheological property, and a method for preparing the blend injection product of thermoplastic cellulose and aliphatic copolyester with special rheological property.

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 that plants convert carbon dioxide and water in the atmosphere into carbon dioxide and water through photosynthesis, carbon elements in cellulose belong to recently fixed carbon and are different from carbon elements fixed millions of years ago in fossil fuels such as petroleum or coal and petrochemical products thereof, and carbon elements fixed at different periods can pass through¹⁴C isotope calibration methodAnd (6) detecting. Due to the differences, the bio-based polymer product prepared based on the biomass raw material has the advantage of low carbon of the raw material compared with the petroleum-based polymer product, and the green low-carbon polymer product 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 derivatives thereof, are receiving increasing attention and research and development in the world 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 injection molded articles 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 property, and successfully applies the blend to the field of injection molding products, wherein the obtained blend material has better injection molding performance than the starting raw material.

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 to be applied to the injection molding field of injection molded products needing low melt viscosity in the prior art, and provides an injection molded product of the blend of the thermoplastic cellulose and the aliphatic copolyester with special rheological property, and the injection molded product adopts the blend material of the thermoplastic cellulose and the aliphatic copolyester to effectively reduce the viscosity of the blend to be lower than the theoretical viscosity of the blend of the thermoplastic cellulose and the starting raw materials of the aliphatic copolyester in an unexpected way; the blend has the processing performance of being prepared into injection molding products at lower temperature, is superior to the similar blend in the prior art, and can save more energy in the processing process due to low melt viscosity of the blend.

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

In order to solve one of the above technical problems, the technical scheme adopted by the invention is as follows: an injection molded article of a thermoplastic cellulose and aliphatic copolyester blend having specific rheological properties, the blend material comprising 20 to 80% by mass of a thermoplastic cellulose and 80 to 20% by mass of an aliphatic copolyester, wherein the melt viscosity of the mass of the thermoplastic cellulose and the mass of the aliphatic copolyester 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 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).

Aliphatic copolyesters can be prepared from a variety of different aliphatic diacids described above and aliphatic diols by 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 cellulose and aliphatic copolyester blend material with special rheological properties, which is described in any one of the technical schemes, comprises the steps of adopting melt blending, and uniformly mixing the required amount of thermoplastic cellulose and the required amount of aliphatic copolyester in a molten state to obtain the thermoplastic cellulose and aliphatic copolyester blend material with special rheological properties.

In the above technical solution, the method is preferably a twin-screw continuous extrusion method.

In the technical scheme, the method preferably comprises the steps of continuously extruding and granulating the thermoplastic cellulose powder, blending the thermoplastic cellulose powder with 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 method 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 double-screw extruder according to the required feeding proportion to perform extrusion granulation.

In the technical scheme, the method preferably comprises the step of respectively metering the thermoplastic cellulose powder and the aliphatic copolyester into a double-screw extruder according to a certain feeding proportion to perform extrusion granulation.

In the above technical solution, the screw rotation speed of the method is preferably 50rpm to 1500rpm.

In the above technical solution, the temperature of the method is preferably 140 ℃ to 240 ℃.

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 andgloss, etc. 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 basis for judging the compatibility between the components [ multicomponent polymer-principle, structure and performance, King's institute of construction and edition, 2013, p.20-22 ], if the blend respectively keeps the glass transition temperature of the raw material components, the phase between the components is shownThe compatibility is poor, whereas a blend with only one glass transition temperature indicates a better compatibility between the components. 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 have not been reported in a blend system with good compatibility, and if the phenomena can be applied in a system with good compatibility, the phenomena have great potential.

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.

A blend of a particular embodiment of the invention comprises cellulose acetate butyrate ester and a biodegradable polyester such as an aliphatic copolyester, preferably polyethylene glycol adipate succinate (PESA), polypropylene glycol adipate succinate (PPSA)) Polybutylene succinate adipate (PBSA), polybutylene succinate adipate (PHSA), and the like, which 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 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.

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 high in 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 melt index of the blend is 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 that is lower than the theoretical value of the additive mixing of pure thermoplastic cellulose and aliphatic copolyester starting materials, i.e., exhibit a "concave" curve in the "apparent Viscosity-composition" relationship, which is manifested by the phenomenon of "Melt Viscosity trap" (Melt Viscosity Well), indicating that the blends have an "Anti-Synergistic Effect" (Anti Effect or Anti-synthetic 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 blend have a melt viscosity at least 50% lower than the theoretical value of the combined addition of the two starting materials, and some most preferred compositions (mass ratio of copolyester to thermoplastic cellulose 50%: 50% to 35%: 65%) of the blend have a melt viscosity at least 60% lower than the theoretical value of the combined 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 injection molding product

The invention discloses a method for preparing a thermoplastic cellulose and aliphatic copolyester blend injection molding product with special rheological property, 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) At least 30% lower than the theoretical value of addition under the conditions. The blend has better injection molding processing performance than the initial raw material, in the method, the blend is plasticized and melted on an injection molding machine and then is injected into a mold cavity by an injection screw, and the blend melt is separated from an injection mold after being cooled in the mold cavity under certain pressure and dwell time to form an injection molding product.

In the injection molding process, the blend of the present invention is fed into a screw-type injection machine through a hopper, the barrel of the injection machine is heated to a temperature suitable for 160 ℃ to 240 ℃ and more suitably 180 ℃ to 220 ℃ by an electric heating system.

In an injection cycle, the injection machine plasticizes and melts the blend by the mechanical energy of the screw rotation and the thermal energy provided by the heating cylinder, and injects a mass of the blend melt into a closed mold cavity at a pressure and speed for a certain period of time; after injection, the screw continues to apply pressure and maintain a constant pressure (dwell pressure) to increase the density of the blend melt to avoid shrinkage of the injection molded article, with dwell pressures of 5 bar (0.5MPa) to 2000 bar (200MPa) being suitable. The mold then enters a cooling stage, where cooling is accomplished by a cooling fluid (water or other liquid) flowing in a cooling line in the injection mold, suitably at a mold temperature of 5 ℃ to 100 ℃, more suitably at a mold temperature of 10 ℃ to 80 ℃, and most suitably at a mold temperature of 20 ℃ to 60 ℃. The cooling time in the mold is 1 second to 200 seconds, more preferably 5 seconds to 100 seconds, and most preferably 10 seconds to 80 seconds. The cooled injection molded article is released from the mold by an ejector pin (ejector).

The blend of the present invention is injection molded into articles including various sizes and shapes. The blends of the invention allow the preparation of very thin injection-molded articles due to their special rheological properties. The preferred thickness of the injection molded articles of the present invention is from 100 micrometers to 50 millimeters, in some embodiments from 250 micrometers to 25 millimeters, and in still other embodiments from 500 micrometers to 5 millimeters.

The injection molded articles of the present invention include single layer injection molded articles and double or multilayer injection molded articles. The double-layer injection molding machine comprises two independent injection molding systems: 1) an injection molding machine, which is responsible for injecting the core of the double injection molded article, can inject the blend of the invention with special rheological properties; 2) and an injection molding machine is used for injecting the surface layer part of the double-layer injection molding product, the thermoplastic surface layer material is added into the injection molding machine, and the injection molding machine performs injection, pressure maintaining and cooling in a second mold cavity provided with the core layer to form the surface layer, so that the double-layer injection molding product is prepared. Wherein the skin portion may be the specific blend of the present invention but has a different composition from the core portion of the injection molded article, for example, the skin portion may be a blend containing 20% by mass of a thermoplastic cellulose and 80% of an aliphatic copolyester; the core part contains 60 mass percent of thermoplastic cellulose and 40 mass percent of aliphatic copolyester; another embodiment is that the skin material is a completely different material from the present invention, such as low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, polyolefin elastomer, ethylene propylene rubber, polyethylene terephthalate, polyamide, polyurethane, etc.

The thickness of the core layer in the two-layer injection molded article is 95 to 55% of the total thickness of the two-layer injection molded article (including the core layer and the skin layer). One embodiment is a two-layer injection molded article wherein the core layer has a thickness of 90 to 60% of the total thickness of the two-layer injection molded article. Yet another embodiment is a two-layer injection molded article wherein the core layer has a thickness of 80 to 65% of the total thickness of the two-layer injection molded article.

The surface layer portion of the injection molded article has physical properties, chemical properties, mechanical properties, etc. different from those of the core portion due to the difference in composition, and it is a specific embodiment of the present invention that the surface layer portion of the injection molded article has higher toughness than the core portion, and the injection molded article is less likely to be damaged by external stress and impact. Another embodiment is that the surface portion of the injection-molded article has a higher degree of wear resistance than the core portion, and the injection-molded article is less susceptible to damage from external mechanical wear. Multilayer injection molded articles have a wider range of applications than single layer injection molded articles. By making a bi-layer injection molded article, we can effectively incorporate a green, low carbon thermoplastic cellulosic material into an injection molded article. The twin screw extrusion temperature of the blend injection molded article is from 140 ℃ to 240 ℃, preferably from 160 ℃ to 220 ℃. The number of revolutions of the twin-screw extruder is 10 to 500rpm, preferably 20 to 300 rpm.

The thermoplastic cellulose and aliphatic copolyester blend injection molding product prepared by the continuous extrusion blending method disclosed by the invention has lower melt viscosity, higher melt index and good compatibility than the theoretical value of the mixing addition of two pure raw materials, the injection molding performance of the blend is better than that of the initial raw material, the injection molding product with large volume and thin wall thickness can be prepared, the application potential is wide, and the better technical effect is obtained.

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 injection molded bars of PBSA/CAB particles.

FIG. 10 DSC cooling curves for each PLA/CAB particle.

FIG. 11 DSC second temperature rise profile for each PLA/CAB particle.

FIG. 12 the relationship between melt index (190 ℃,2.16kg) and composition for each PLA/CAB particle.

FIG. 13200 ℃ graph of apparent shear viscosity versus shear rate for each PLA/CAB particle.

Graph at 14200 ℃ for 100s for each PLA/CAB particle^-1The apparent shear viscosity versus composition at shear rate of (3).

At 15200 ℃ for each PLA/CAB particle at 1363s^-1The apparent shear viscosity versus composition at shear rate of (3).

FIG. 16 DSC cooling curves for each PBS/CAP particle.

FIG. 17 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, processing softwareIs Launch

Version 8.60. The test uses a sensor with 10000Psi pressure and a 16/1.0/180 round hole type capillary die. 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 (". DELTA.H "), etc.

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

MD 3001 PBSA 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

MD 3001 PBSA 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 a feeding port to a die, the number of the sections is 1-11, wherein the 1 st section is only addedThe material is 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 ]

MD 3001 PBSA 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 MD 3001 PBSA 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 melt index of the particles at 190 ℃ under 2.16kg was 3.73g/10 min.

[ example 2 ]

MD3001 PBSA 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 MD 3001 PBSA 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 MD 3001 PBSA 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 ℃,150 ℃,160 ℃,160 ℃,160 ℃,160 ℃ and 160 ℃, the screw rotation speed is set at 200rpm, and the torque is 41-43%. 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 granuleAnd vacuumizing in a vacuum drying oven 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 MD 3001 PBSA 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 MD 3001 PBSA particles at the speed of: 420g/hr, while the calibrated volumetric powder feeder is used in Eastman^TM CAB-381-0.5, feeding 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 Rosand RH7 hot high pressure capillary rheometer, the test methods 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 temperature decrease curves and the second temperature increase curves are shown in fig. 4 and 5. The crystallization temperature ("T") can be directly derived therefrom by software_c"), melting temperature (" T ")_m"), glass transition (" T ")_g"), enthalpy change (". DELTA.H "), and the like, and specific values are shown in Table 2. Glass transition temperature ("T") of each particle_g") versus composition is shown in fig. 6.

It can be seen from fig. 4 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, and only the second temperature rise curve of example 1 has a crystallization peak (fig. 5), but the crystallization temperature and the peak area are both lower than those of pure PBSA particles, and the corresponding melting peak temperature and area are also lower than those of pure PBSA particles (see table 3 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. 7. 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. 8. 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 ]

Particles prepared in examples 1-5 and comparative examples 1-2 were HAKKE from Thermo Fisher scientific Co., USA^TMInjection molding experiments were performed in a MiniJet II micro injection molding machine. The mold is a 557-2295-60 × 10 × 1 mold produced by Thermo Fisher science and technology, and the temperature of the material cavity and the temperature of the mold in the experimental process are respectively set as follows: 190 ℃ and 50 ℃. Setting the pressure at 300bar in the injection molding process for 5s, maintaining the pressure at 100bar for 20s in the subsequent pressure maintaining process, demolding, and collecting injection molded sample bars.

Under the same injection molding conditions, the injection molding properties of the materials are obviously different due to the difference of the flow properties of the materials. The size of the sample obtained by injection molding shows the difference in injection molding processability. All 7 injection molded bars are shown in fig. 9, where the shortest injection molded bar was produced from the starting PBSA starting material (comparative example 1) and the starting CAB starting material (comparative example 2), indicating that the flow of the starting materials was the lowest. Whereas the injection molded bars made from all blends of the present invention were longer than the injection molded bars made from comparative example 1 and comparative example 2, indicating that the injection molding performance of the raw material was greatly improved due to the improved flow properties of the blends, with the injection molding performance of example 1 being the best. Due to the improved rheological properties of the blends, the blends of the invention allow the production of larger injection-molded parts under the same conditions. While high flowability also offers the possibility of producing more injection-molded articles in the same time.

From the results of example 10, it is also fully demonstrated that the unexpected blending of two low flow feedstocks (PBSA feedstock and CAB feedstock) of the present invention, resulting in a blend with high flow, is beyond our expectations.

Comparative example 3

Adopts aliphatic polyester polylactic acid (Nature Works Ingeo)^TM4032D) With thermoplastic cellulose CAB (Eastman)^TMCAB-381-0.5) is subjected to melt blending extrusion by the same processing method, and PLA is not aliphatic copolyester described in the invention. 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-mentioned procedures, and the temperature decrease curves and the second temperature increase curves are shown in fig. 10 and 11. It is evident from FIGS. 10 and 11 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^TM4032D PLA 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

MD 3001 PBSA and Eastman^TMCAB-381-0.5 blend only has one glass transition temperature ("T_g") that is

MD 3001 PBSA 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 ℃,2.16kg according to the method described above, and the results are shown in fig. 12; in addition, each PLA/CAB particle was measured for capillary rheology at 200 ℃ as described above and the results are shown in FIG. 13, 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. 14 and 15, respectively. From FIG. 12, 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. 13 that the viscosity curve of most mixed particles is between two pure raw materials, and in fig. 14 and fig. 15, although there are cases where the viscosity of the blend is smaller than the mixing addition theoretical value in a narrow range, the PLA/CAB blended particles have difficulty in satisfying 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 OS PTW16 co-rotating twin-screw extruder, and proportionally and simultaneously adding into the 1 st section of the extruder by using a volumetric feeder of the extruder

MD 3001 PBS 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 PBS/CAP particles were subjected to DSC test according to the method described above, and the cooling curve and the second heating curve are shown in fig. 16 and fig. 17, respectively. It is apparent from FIGS. 16 and 17 that the PBS and CAP materials remain in their respective crystallization and melting processes after mixing, except that the crystallization temperature of PBS rises from about 80 ℃ for the 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.

[ example 11 ]

Injection molding of the PLA/CAB blend pellets was also carried out under the conditions described in example 10 above, and it was found that due to their higher melt viscosity, no complete injection molded bars could be obtained at the same time, and that higher injection pressures or longer injection times were required to obtain defect-free injection molded bars. 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 injection molding.

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 ℃ C. at a shear rate of 1363s^-1Measured apparent shear viscosity, theoretical apparent shear viscosity, and difference and percentage difference between the two

TABLE 3 thermal Properties of the particles 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

Claims

1. An injection-molded article of a blend of a thermoplastic cellulose and an aliphatic copolyester, the blend injection-molded article comprising 20 to 80% by mass of a thermoplastic cellulose and 80 to 20% by mass of an aliphatic copolyester, characterized in that the melt viscosity of the blend of the thermoplastic cellulose and the aliphatic copolyester is 100s at a low shear rate^-1Under 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 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 aliphatic copolymer is polybutylene succinate adipate; the thermoplastic cellulose is cellulose acetate butyrate.

2. An injection molded article of a thermoplastic cellulose and aliphatic copolyester blend as claimed in claim 1, characterized in that the number average molecular weight of the blend is at least more than 20000g/mol and the weight average molecular weight is at least more than 60000 g/mol.

3. A process for preparing the thermoplastic cellulose and aliphatic copolyester mixture injection-molded product as claimed in claim 1 or 2, wherein the required amount of thermoplastic cellulose and aliphatic copolyester is plasticized and melted in an injection-molding machine, and then injected into a mold cavity by an injection screw, and the melt of the mixture is subjected to pressure maintaining and cooling in the mold cavity and then separated from the injection-molding mold to form the injection-molded product.

4. A process for preparing the thermoplastic cellulose and aliphatic polyester blend injection-molded product of claim 1 or 2, wherein the first raw material or blend is fed into a two-material co-injection molding machine, plasticized and melted, and then injected into a mold cavity by an injection screw, and after pressure maintaining and cooling, the first raw material or blend is separated from the injection mold to form a core layer of the injection-molded product, and the second thermoplastic skin material or blend is fed into another injection molding machine and injected, pressure maintaining and cooling into another mold cavity with the core layer to form a skin layer, thereby preparing a two-layer injection-molded product; the double-layer injection molding product is characterized in that one layer is a blend of thermoplastic cellulose and aliphatic copolyester, and the other layer is other materials suitable for injection molding; or the double-layer injection molding product is formed by mixing two layers of thermoplastic cellulose and aliphatic copolyester, and the two layers of the thermoplastic cellulose and aliphatic copolyester blends have different composition ratios.