CN1037515C - Biodegradable starch-containing polymer composition and preparation method thereof - Google Patents

Abstract

The invention relates to a biodegradable starch-containing polymer composition, a production method thereof and application of a product thereof. The composition has the advantages of easily available raw materials, low cost, no toxicity, simple processing technology, mechanical property close to that of polyethylene, biodegradation of the product within a certain time, and granular residue.

Description

Biodegradable composition containing starch and its producing method and its use

The production method that the present invention relates to a kind of biodegradable amyloid polymeric composition and it with and the purposes of goods.

The range of application of plastics and quantity enlarge at present just day by day, and have brought huge social benefit and economic benefit, but along with the increasing of plastic refuse, have also caused the serious environmental pollution problem.This mainly is owing to remain in due to plastic refuse in the physical environment decomposes very slowly.The problem of environmental pollution of plastics has caused the extensive attention of countries in the world, and has carried out number of research projects and solved this problem.

Have for addressing this problem the measure of taking at present: one, reclaim, burn, bury.The method that adopt to reclaim will expend lot of manpower and material resources, also needs various plastics are separated, classify, and be difficult for carrying out, and this method can not reclaim plastic refuse fully, residually remains very serious; Adopt the method for burning, not only have an economic benefit, problem also can produce toxic gas and heavy-metal residual, causes secondary pollution; The method that employing is buried will take a large amount of places, and the decomposition course of plastics is very slow, and some needs one, bicentenary time just can decompose fully, so this neither effective means.Two, development degradative plastics.Degradative plastics comprises photodegradation and biodegradable plastic etc. substantially.Generally contain reactive group in the photodegradable plastics or be added with photosensitizers, make the macromolecular chain fracture, reach the purpose of degraded by absorbing ultraviolet ray.The shortcoming of photodegradable plastics is the cost height, and degradation speed is wayward, and buried can not the degraded.Adopting biodegradable plastic is efficient ways the most.Biodegradable plastic can be divided into direct synthesis type and composition type two classes.Directly the synthesis type biodegradable plastic is that biodegradable polymkeric substance can take place a class itself, is characterized in containing on the molecular chain or can changing into other group of above-mentioned group by the group of microbial attack.As polyester PHB and PHBV, can be degraded by microorganisms, be more satisfactory up to now Biodegradable plastic.It is too high that but their shortcoming is a cost, causes very big difficulty to application.Composition type biodegradable plastic is that biodegradable material and the material hybrid process that is difficult for degraded are made, after the degradable thing is consumed, the material that is difficult for degraded becomes fragment or particle, reach the purpose of decontamination with this, this is the most promising at present class biodegradable plastic.As at EP-0400531, in several pieces of patents such as EP-0421413 and EP-0444880, biodegradable starch is mixed with the macromolecular compound that is difficult for degraded, biological degradation can take place in resulting composition.But the ubiquitous shortcoming of present amyloid composition type degradative plastics is the complete processing complexity, and starch content is low, so cost is higher, and degradation rate and degradation speed are undesirable.Improve degradation rate, need the addition of starch is increased, but consequent problem be the mechanical property of composition can be worse and worse along with the increase of amount of starch.Someone improves mechanical property by adding treated starch, and effect is also not obvious.

The objective of the invention is to propose a kind of is that main raw material and synthetic macromolecular compound mix with general industry starch, obtain a kind of biodegradable method for compositions by adding proper assistant and suitable processing means, can carry out the industrialization continuous production, and can overcome the deficiency of this type of material in the past, make composition be applicable to purposes such as blown film, injection moulding, satisfy the requirement of tensile strength, elongation, angle tear strength, transmittance and biodegradation rate.

Main contents of the present invention comprise:

Biodegradable polymeric composition, it consists of: (a) starch; (b) polyethylene; (c) ethylene-acrylic acid copolymer (EAA); (d) polyvinyl alcohol; (e) ethylene-vinyl acetate copolymer (EVA); (f) calcium stearate; (g) polyvalent alcohol; (h) urea; (i) alkali; (j) tensio-active agent; (k) deionized water.

With ZSK series twin screw extruder (U.S. Werner﹠amp; Pfleiderer company produces) and the various components that will accurately measure of corresponding dynamic continuous measurement feed system carry out hybrid process by a certain percentage, carry out granulation, blown film, pulling-on piece, injection moulding, foaming etc. with conventional device of plastic processing.

Starch is the general industry product, water content 10-13%, and granularity is thin more, easy more gelatinization, the hybrid process effect is good more; Polyethylene is the mixture of new LDPE (film grade) (LDPE) or linear low density polyethylene (LLDPE) or two kinds, and melting index is 0.5-20; Acrylic acid content is 5-25% among the EAA; Enol content is that 10-30%, polyvalent alcohol can be ethylene glycol, propylene glycol, glycerol, sorbyl alcohol or several mixtures among the EVA; Alkali can be sodium hydroxide, ammonium hydroxide, trolamine; Tensio-active agent can be ionic or nonionic surface active agent.

The weight percentage of each component concentration is in the biodegradable polymeric composition:

(a) starch 20-70

(b) polyethylene 0-55

(c)EAA 5-35

(d) polyvinyl alcohol 0-30

(e)EVA 0-30

(f) calcium stearate 0.3-2

(g) polyvalent alcohol 5-20

(h) urea 0-2

(i) alkali adds in the liquid ingredient, and adjust pH is to 10-12.5

(i) tensio-active agent 0.1-1

(k) deionized water balance amount

It is as follows to mix expressing technique:

Processor is a ZSK series twin screw extruder, accurately controls the ratio of each component with the dynamic continuous measure feed system.

1. at first aforementioned (g), (h), (j) component and deionized water being mixed, is 10-12.5 with the pH value of alkali regulator solution, and liquid ingredient by in the volume pump adding forcing machine, is added starch then, makes starch pasting.Set each interval temperature of forcing machine and be this moment: I80-90 ℃; II80-100 ℃; III80-100 ℃; IV80-100 ℃; V80-100 ℃, VI80-100 ℃.Screw speed is 150-200rpm.

2. starch to be extruded become transparent after, add EAA or EVA or polyvinyl alcohol, be increased to each interval design temperature this moment: I80-90 ℃; II100-120 ℃; III100-120 ℃; IV100-120 ℃; V100-120 ℃; VI100-120 ℃.Screw speed is 150-250rpm.

3. when treating that the die head place finds to have EAA to occur, add polyethylene, this moment, each interval temperature of forcing machine was set at: I90 ℃; II120-130 ℃; III120-130 ℃; IV120-130 ℃; V120-130 ℃; VI120-135 ℃.Screw speed is 250-350rpm.

Extrude in stable condition after, the air cooling of strip extrudate can be extruded, pelletizing continuously.

Polymeric composition of the present invention can be used for making agricultural film, shopping bag, refuse bag, disposable tableware, various wrapping material (as film, porous plastics etc.), disposable sanitary articles, stationery, seedling-raising cup etc.

The invention has the advantages that:

1. be suitable for the industrialization continuous production.

2. the mechanical property of composition approaches polyethylene, can produce various goods, particularly can carry out blown film processing under the situation of high-content of starch, the intensity of the film of producing, elongation, printing opacity degree and good air permeability.

3.ZSK the length-to-diameter ratio of serial twin screw extruder reaches as high as 48: 1, compares with general forcing machine, length-to-diameter ratio is much bigger; The screw speed height reaches as high as 500rpm; The combination of cord wood screw element can change arbitrarily according to the processing needs, and good mixing effect can reach each component uniform distribution.

4. because each component homodisperse, after starch was degraded, plastics had become very small fragment or particle, therefore needn't expend the recovery operation that great amount of manpower and material resources is carried out waste, residue can not pollute the soil yet, also can increase the ventilation property of soil on the contrary.

5. complete processing is simple, and various raw materials need not carry out pre-treatment, and conventional device of plastic processing can meet the demands when carrying out goods processing, does not have too much new technical problem.

6. raw material is easy to get, and product cost is low.

7. various raw materials are all nontoxic, meet the food sanitation requirement.

Embodiment 1:

Component weight percentage (%)

Starch 25.0

Polyethylene 52.3

EAA 8.0

Glycerol 10.0

Calcium stearate 0.5

Sodium laurylsulfonate 0.2

Sodium hydroxide is transferred liquid pH value to 11

Deionized water 4.0

Fabrication process condition:

(1) glycerol, sodium laurylsulfonate are mixed with deionized water, hydro-oxidation sodium is regulated pH value to 11, adds in the forcing machine by volume pump, adds starch then, makes starch pasting.Set each interval temperature of forcing machine this moment is I-VI80 ℃.Screw speed 150rpm.

(2) starch to be extruded transparent after, add EAA, each interval temperature of rising forcing machine is I90 ℃; II-VI100 ℃.Screw speed degree 225rpm.

(3) treat that the die head place has EAA to occur after, add polyethylene, each interval temperature of forcing machine is: I90 ℃; II-V120 ℃; VI125 ℃.Screw speed degree 300rpm.

(4) the strip extrudate carries out pelletizing through air cooling.

The processing condition of other prescription similarly only need to carry out the part adjustment according to the difference of prescription.

Embodiment 2:

Component weight percentage (%)

Starch 30.0

Polyethylene 46.0

EAA 13.5

Sorbyl alcohol 5.7

Calcium stearate 0.6

Sodium hydroxide is transferred liquid pH value to 11.5

Deionized water 4.2

Embodiment 3:

Component weight percentage (%)

Starch 42.5

Polyethylene 18.0

EAA 26.0

Glycerol 8.3

Calcium stearate 0.9

Sodium hydroxide is transferred liquid pH value to 11

Deionized water 4.3

Embodiment 4:

Component weight percentage (%)

Starch 51.0

Polyethylene 14.2

EAA 17.4

Sorbyl alcohol 9.3

Calcium stearate 1.1

Urea 1.7

Peregal 0.1

Sodium hydroxide is transferred liquid pH value to 11.5

Deionized water 5.2

Embodiment 5:

Component weight percentage (%)

Starch 62.7

Polyethylene 8.0

EAA 15.0

Sorbyl alcohol 7.0

Calcium stearate 1.3

Sodium hydroxide is transferred liquid pH value to 11.5

Deionized water 6.0

Embodiment 6:

Component weight percentage (%)

Starch 39.4

EAA 24.2

EVA 24.2

Sorbyl alcohol 6.8

Calcium stearate 0.9

Deionized water 4.5

The result that above embodiment sample is carried out Mechanics Performance Testing is as follows:

Sample 123456

Tensile strength (MPa) 22.0 24.1 21.5 14.6 13.8 9.2

Elongation at break (%) 347 305 246 144 114 81.3

Claims (2)

1. biodegradable amyloid polymeric composition comprises:

(a) the 20-70% water content is the starch of 10-13%;

(b) the 8-55% melting index is new LDPE (film grade) or linear low density polyethylene or its mixture of 0.5-20;

(c) the 5-35% acrylic acid content is the ethylene-acrylic acid copolymer of 5-25%;

(d) 0-30% polyvinyl alcohol;

(e) 0-30% enol content is the ethylene-vinyl acetate copolymer of 10-30%;

(f) 0.3-2% calcium stearate;

(g) 5-20% is selected from the polyvalent alcohol of ethylene glycol, propylene glycol, glycerol, sorbyl alcohol or its mixture;

(h) 0-2.0% urea;

(i) be selected from alkali in the group that sodium hydroxide, ammonium hydroxide, trolamine or its mixture form, its consumption makes the pH value of the liquid ingredient of composition be adjusted to 10-12.5;

(i) 0.1-1% is selected from ionogenic surfactant or nonionic surface active agent;

(k) deionized water of equal amount;

Wherein, described percentage ratio is meant the percentage ratio of each ingredients constitute composition total weight.

2. the preparation method of a biodegradable amyloid polymeric composition may further comprise the steps:

(1) selection is provided with the ZSK series twin screw extruder in I, II, III, IV, V, six intervals of VI;

(2) will account for the ethylene glycol that is selected from of composition total weight 5-20%, propylene glycol, glycerol, the polyvalent alcohol of sorbyl alcohol or its mixture, the tensio-active agent that is selected from ionogenic surfactant or nonionic surface active agent of the urea of 0-2.0% and 0.1-1% mixes with the deionized water of equal amount, and adding is selected from sodium hydroxide, ammonium hydroxide, alkali in the group that trolamine or its mixture are formed is 10-12.5 to regulate its pH value, this liquid mixture is joined in the forcing machine by volume pump, adding the 20-70% water content that accounts for composition total weight then is the starch of 10-13%, and the temperature of setting six intervals in the forcing machine is as follows: interval I:80-90 ℃; Interval II-VI:80-100 ℃; Screw speed is 150-200rpm, makes starch pasting thus;

(3) make the starch of extruding transparent after, adding the acrylic acid content account for composition total weight 5-35% is that the ethylene-acrylic acid copolymer of 5-25% or the enol content of 0-30% are the ethylene-vinyl acetate copolymer of 10-30% or the polyvinyl alcohol of 0-30%; Set each interval temperature of forcing machine and be this moment: interval I:80-90 ℃; Interval II-VI:100-120 ℃; Screw speed is 150-280rpm;

(4) when the die head place finds to have ethylene-acrylic acid copolymer to occur, adding accounts for new LDPE (film grade) or the linear low density polyethylene that composition total weight 8-55% melting index is 0.5-20 and becomes its mixture; Set each interval temperature of forcing machine and be this moment: interval I:90 ℃; Interval II-V:120-130 ℃; Interval VI:120-135 ℃; Screw speed is 250-350rpm;

Make extrude in stable condition after, the air cooling of strip extrudate is extruded, pelletizing continuously.