CN104817752A - Polyethylene thin film and preparation method thereof - Google Patents

Abstract

The invention discloses a polyethylene thin film, of which the technical parameters are described as follows: the thickness is not more than 40 [mu]m; the longitudinal tensile strength is not less than 70; the transversal tensile strength is not less than 120; the longitudinal elongation at break is not less than 310; the transversal elongation at break is not less than 70; the longitudinal heat shrinkage is not more than 4; the transversal heat shrinkage is not more than 4; and the haze is not more than 4.8. The polyethylene thin film is prepared through a bidirectional stretching method, so that the polyethylene thin film is less in required raw materials and is environment-friendly, which are the characteristics of the bidirectional stretching method. In addition, the performance parameters of the polyethylene thin film can reach even exceed those of a common polyethylene thin film even the thickness is reduced.

Description

A kind of polyethylene film and preparation method thereof

Technical field

The present invention relates to polyethylene film and preparation method thereof, be specifically related to standby polyethylene film of a kind of two-way stretch legal system and preparation method thereof.

Background technology

Polyethylene (be called for short PE) be ethene through being polymerized obtained a kind of crystalline thermoplastic resin, industrially, also comprise the multipolymer of ethene and a small amount of alpha-olefin.Polyethylene odorless, nontoxic, feel ceraceous, fusing point is 100-130 DEG C.Its resistance to low temperature is excellent, at-60 DEG C, still can keep good mechanical property, but use temperature is at 80 ~ 110 DEG C; Chemical stability is good, the erosion (the not resistance to acid with oxidizing property) of the most of soda acid of ability.Be insoluble to common solvent under normal temperature, water-absorbent is little, and electrical insulating property is excellent.

Poly chemical structure, molecular weight, the polymerization degree and other performances all depend on the polymerization process of use to a great extent.Polymerization process determines type and the side chain degree of side chain.Degree of crystallinity depends on alignment degree and its thermal history experienced of part molecular chain.Polyethylene, according to the difference of polymerization process, molecular weight height, chain structure, divides high density polyethylene(HDPE), Low Density Polyethylene and linear low density polyethylene.Low Density Polyethylene (LDPE) is commonly called as high-pressure polyethylene, it is at high pressure (100-300MPa), high temperature (190 – 210C), under peroxide catalyzed condition, radical polymerization is produced, and it is side chain chemical combination structure.Because density is lower, material is the softest, is mainly used in polythene bag, film for agricultural use etc.High density polyethylene(HDPE) (HDPE) is commonly called as low pressure polyethylene, and it carries out Ziegler-Natta and is polymerized under lower pressure (15-30 normal atmosphere) organic compound catalytic condition; The polyethylene molecule be polymerized under this condition is linear, and molecular chain is very long, and molecular weight is up to hundreds of thousands of.HDPE and LDPE and LLDPE compares, and has higher heatproof, oil-proofness, resistance to vapour permeability and environmental stress crack resistance, in addition electrical insulating property and shock resistance and cold tolerance fine, be mainly used in the field such as blowing, injection moulding.LLDPE (LLDPE) is then the multipolymer that ethene and a small amount of senior Α-alkene are polymerized in the presence of a catalyst.The advantages such as LLDPE outward appearance is similar to LDPE, and the transparency is more poor, and only surface luster is good, has low-temperature flexibility, high-modulus, counter-bending and stress cracking resistance, and under low temperature resistance to impact shock is better.LLDPE performance is similar to Low Density Polyethylene, and has some characteristics of high density polyethylene(HDPE) concurrently, and in producing, energy expenditure is low in addition, therefore develops very rapid, becomes one of the most compelling new synthetic resins.

Polyethylene film adopts blow moulding or casting method to make usually, and Biaxial tension polyethylene film is a kind of PE film newly developed, is to adopt the method for flat embrane method diaxial orientation step drawing complete processing to carry out the film produced.At present, diaxial orientation step drawing technique is mainly used in the production of the films such as PP film, PA film and PET film; But PE cannot use this explained hereafter due to structure itself and crystallization situation.Biaxially oriented film has the following advantages relative to general thin: 50% film lightweight, the thickness of packaging base material can be made to reduce by 50%, therefore can save ample resources, and reduce costs significantly; The friendly of environment: saving resource, reduces the discharge of CO2, renewablely to recycle, does not use tackiness agent; User friendly: possess line easy-tear performance, tearing notch is neat; Above the ordinary resistance to low temperature, has excellent shock-resistant and anti-pin hole performance under low-temperature condition.

In view of the film that two-way stretch legal system is standby can be implemented in identical performance condition compared with film prepared by traditional method under reduce poly a small amount of and therefore its correlation parameter can't reduce, thus use the standby film of this legal system have lower cost compared with film prepared by traditional method and also can reduce environmental pollution.

Summary of the invention

The object of the invention is to solve the problem, a kind of polyethylene film of the excellent performance standby by two-way stretch legal system is provided.

In order to achieve the above object, scheme of the present invention is:

A kind of polyethylene film, it is characterized in that, described polyethylene film thickness is less than or equal to 40um, longitudinal tensile strength is more than or equal to 70, and transverse tensile strength is more than or equal to 120, and longitudinal fracture elongation is more than or equal to 310, transverse breakage elongation is more than or equal to 70, longitudinal thermal contraction is less than or equal to 4, and horizontal thermal contraction is less than or equal to 4, and mist degree is less than or equal to 4.8.

Preferably, described polyethylene film is standby by two-way stretch legal system; Prepare the polyethylene product that polyethylene film uses to be prepared by polyvinyl resin and nucleator and additive; The MFR:80-120g/10min of described polyvinyl resin, Cr content is less than 3PPMW, and Ti content is less than 3PPMW, nucleator content 0.05-0.3%.

Preferably, described polyvinyl resin is by chromium-based catalysts catalyzed polymerization, and described chromium-based catalysts is made up of silicon-dioxide, chromic oxide, titanium oxide, silicon fluoride and organic chromium, SiO ₂content is more than or equal to 85%, Ti content and is more than or equal to 8%, Cr content and is more than or equal to 1%, and activity is more than or equal to 5000 times.

The preparation method of above-mentioned polyethylene film, described preparation method comprises the following steps:

(1) granulation after polyvinyl resin and additive, nucleator being mixed by proportioning high-speed stirring; Additive is Irganox 1010 and Irgafos 168, and both account for total weight percent and are 0.05-0.10%, and nucleator is sorbyl alcohol, inorganic salt, organic salt, and it is 0.05-0.3% that nucleator accounts for total weight percent.

(2) drop in two-way stretch film-making machine by above-mentioned particle, after setting, thickness is less than or equal to 40um, then makes polyethylene film.

Preferably, described nucleator is organic calcium salt.

Polyethylene film of the present invention is standby via two-way stretch legal system, and it possesses the few and eco-friendly feature of materials that two-way stretch method has; Further, when thickness reduces, it still can reach the various performance parameters even surmounting Plain PE film and possess.

Embodiment

Below, be described in detail in conjunction with specific embodiments to the present invention, to make those skilled in the art, the present invention may be better understood, thus make clear restriction to protection scope of the present invention.

A kind of polyethylene film, it is characterized in that, described polyethylene film thickness is less than or equal to 40um, longitudinal tensile strength is more than or equal to 70, and transverse tensile strength is more than or equal to 120, and longitudinal fracture elongation is more than or equal to 310, transverse breakage elongation is more than or equal to 70, longitudinal thermal contraction is less than or equal to 4, and horizontal thermal contraction is less than or equal to 4, and mist degree is less than or equal to 4.8.This polyethylene film is standby by two-way stretch legal system; Prepare the polyethylene product that polyethylene film uses to be prepared by polyvinyl resin and nucleator and additive; The MFR:80-120g/10min of described polyvinyl resin, Cr content is less than 3PPMW, and Ti content is less than 3PPMW, nucleator content 0.05-0.3%.Described chromium-based catalysts is made up of silicon-dioxide, chromium dioxide, titanium dioxide, silicon fluoride and organic chromium, and catalyst grain size is D50:20-50um, SiO ₂content is more than or equal to 85%, Ti content and is more than or equal to 8%, Cr content and is more than or equal to 1%, and activity is more than or equal to 5000 times.

Catalyzer adopts following steps preparation: (1) is dry below 200 DEG C by the silica-gel carrier (Davsion957) containing Cr; (2) joined in reactor after silica-gel carrier cooling, add solvent hexane and titanium salt, stir, be then dried to the powder of flowing; (3) in dried product, add fluorine cpd, move in High Temperature Furnaces Heating Apparatus and be heated to be less than 860 DEG C and make it fully activate; (4) joined in reactor after cooling, and added solvent and two luxuriant chromium, stir, be then dried to the powder of flowing, obtain chromium-based catalysts.

Titanium salt is titanium tetrachloride, tetra isopropyl titanium etc.; Fluorine cpd are amido hexa-fluoride, and Davsion957 is commercial silica-gel carrier.

Design 9 experiments by above preparation method, the condition of each experiment is as shown in table 1.

Table 1 catalyst preparing

In order to carry out polymerization evaluation to the catalyzer prepared by above-mentioned each experiment, the catalyzer of sample 1 to sample 9 is all carried out gas phase catalytic reaction by following condition, the polyethylene performance that each laboratory sample catalysis obtains is as shown in table 2.

Polymerizing condition: temperature of reaction: 85 DEG C; Reaction pressure: 2.1MPa; C4/C2:0.1; H2/C2:0.07.

Table 2 is polymerized to be evaluated

Sequence number	Project	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5	Sample 6	Sample 7	Sample 8	Sample 9
											1	MI	2.7	3.6	2.8	3.4	2.5	1.2	3.2	3.5	3.0
2	MFR	120	109	111	106	119	85	110	97	130
											3	D	925	923	924	921	917	921	925	927	935
4	Active	4500	5000	4700	4200	4050	3200	5000	5500	5600

In addition, in order to the validity that the catalyzer contrasting preparation reacts for polyethylene polymerization, random selecting four sample in contrast in the catalyzer that we are common from the market, comparative example 1,2,3 is three kinds of common Chromium-polyethylencatalyst catalyst, can buy easily, comparative example 4 is commercial a kind of Titanium series catalyst.By four comparative examples catalyzed polyethylene polyreaction under same gas phase polymerisation conditions, the poly performance of each catalyzer gained is as shown in table 3.

Table 3 comparative catalyst is polymerized evaluation

Sequence number	Project	To 1	To 2	To 3	To 4*
						1	MI	1.0	30	0.4	2.0
2	MFR	70	30	78	45
						3	D	920	955	945	918
4	Active	3000	5500	2500	6000

In table 2, table 3: MI refers to that poly MI is melting index, and unit is g/10min; MFR refers to melt mass flow rate, and unit is g/10min; D refers to poly density, and unit is kg/m3; Activity refers to the fold activity that catalyst polyethylene polymerization reacts, generally there are two kinds of method of calculation, a kind of is by the amount of the poly output of gained divided by the catalyzer added, another kind is the inverse getting catalyst residue amount in product, the residual volume of catalyzer in the amount counting yield of the inorganics remained when can be burned by product during measurement, a kind of method of calculation before the many employings in laboratory and a kind of method of calculation after industrial normal use, the present invention adopts front a kind of method of calculation.

Known by the analysis of above experimental data, sample 7 is better samples in each laboratory sample., the catalyzer of sample 7 is tested different gas phase polymerisation conditions respectively below, test conditions and result as shown in table 4:

Table 4 vapor phase process pilot scale polymerizing condition:

Sequence number	Project	Unit	1#	2#	3#	4#	5#*	6#	7#	8#
											1	Temperature	℃	85	80	90	95	85	105	95	85
2	H2/C2	％v	0.07	0.05	0.09	0.07	0.07	0.07	0.07	0.07
											3	C4/C2	％v	0.1	0.1	0.05	0.1	0.1	0.05	0.1	0.1
4	O2	PPb	10	100	300	100	200	0	0	0
											5	MI	g/10min	3.2	2.5	5.0	Caking	1.0	30	0.4	2.0
6	MFR		110	115	105		70	30	78	45
											7	D	Kg/m 3	925	926	930		920	955	945	918
8	Active	10 3	5.0	4.2	3.2		3.0	5.5	2.5	6.0

Vapour phase polymerization preferably polymerizing condition is: polymerization temperature: 80-90 DEG C; H2/C2:0.05-0.09%v; C4/C2:0.05-0.1%v; C4/C6:0.05-0.1%v; O2:0-300ppb.

Catalyzer sample 7 is prepared 7 polyethylene respectively by above-mentioned polymerizing condition, and the polyethylene product specification obtained is as shown in table 5.

Table 5 polyethylene product specification

Sequence number	Project	Unit	F1	F2	F3	F4	F5	F6	F7
										1	MI	g/10min	1.5	1.0	3.0	5.0	3.0	3.0	3.0
2	MFR		70	85	110	105	85	75	150
										3	D	Kg/m3	920	920	925	930	930	920	925
4	ASH	％w	＜0.03	＜0.03	＜0.03	＜0.03	＜0.03	＜0.03	＜0.03
										5	Active	Doubly	3000	3000	5000	3200	4000	3000	Blended
6	Cr	PPM	＜3	＜3	＜3	＜3	＜3	＜0.3	0

To meet the sample of following parameter and additive, nucleator in above-mentioned each polyethylene product by granulation after proportioning high-speed stirring, the sample parameters obtained is in table 6.

Polyethylene product: MI:1-5g/10min;

MFR:80-120g/10min；

D:0.920-0.930g/cm3；

ASH: be less than 0.03%;

Cr content: be less than 3PPMW;

Additive: Irganox 1010:0.05-0.10%;

Irgafos 168:0.05-0.10％；

Nucleator: 0.05-0.30%.

Irganox 1010 and Irgafos 168 is two kinds of common additives, can buy easily; Nucleator is sorbyl alcohol, inorganic salt, organic salt, and organic calcium salt effect is better; Wherein, organic salt is one preferably nucleator; ASH is ash content, i.e. the inorganics that left behind after high temperature sintering of PE.

Table 6 formula of special material

Sequence number	Project	Sample A	Sample B	Sample C	Sample D	Sample E	Sample F
								1	Resin	F1	F2	F3	F4	F5	F6
2	Irganox 1010	0.1	0.1	0.1	0.05	0.1	0.1
								3	Irgafos 168	0.1	0.1	0.1	0.1	0.05	0.1
4	Nucleator	0.1	0.1	0.2	0.05	0.3	0.1

By above-mentioned A ~ F sample, through two-way stretch processing PE film processed, thickness is set as that rear thickness is less than or equal to 40um.Sample A, F can not film forming, and tensile property is poor.B, C, D, E film forming properties is good, and each sample performance is in table 7.

The performance of table 7PE film

Sequence number

Project

Sample B

Sample C

Sample D

Sample E

Contrast 1

1

Tensile strength (vertical/horizontal)

70/120

80/120

75/130

73/120

70/130

2

Elongation at break (vertical/horizontal)

380/210

350/150

310/70

320/110

300/100

3

Thermal contraction (vertical/horizontal)

4/3.2

3.5/3.3

4/3.5

3.1/4

3.9/3.5

4

Mist degree

4.2

3.9

4.8

4.5

5.3

Claims (5)

1. a polyethylene film, it is characterized in that, described polyethylene film thickness is less than or equal to 40um, longitudinal tensile strength is more than or equal to 70, and transverse tensile strength is more than or equal to 120, and longitudinal fracture elongation is more than or equal to 310, transverse breakage elongation is more than or equal to 70, longitudinal thermal contraction is less than or equal to 4, and horizontal thermal contraction is less than or equal to 4, and mist degree is less than or equal to 4.8.

2. polyethylene film according to claim 1, is characterized in that, described polyethylene film is standby by two-way stretch legal system; Prepare the polyethylene product that polyethylene film uses to be prepared by polyvinyl resin and nucleator and additive; The MFR:80-120g/10min of described polyvinyl resin, Cr content is less than 3PPMW, and Ti content is less than 3PPMW, nucleator content 0.05-0.3%.

3. polyethylene film according to claim 2, is characterized in that, described polyvinyl resin is by chromium-based catalysts catalyzed polymerization, and described chromium-based catalysts is made up of silicon-dioxide, chromic oxide, titanium oxide, silicon fluoride and organic chromium, SiO ₂content is more than or equal to 85%, Ti content and is more than or equal to 8%, Cr content and is more than or equal to 1%, and activity is more than or equal to 5000 times.

4. the preparation method of polyethylene film according to claim 1, is characterized in that, described preparation method comprises the following steps:

(1) granulation after polyvinyl resin and additive, nucleator being mixed by proportioning high-speed stirring; Additive is Irganox 1010 and Irgafos 168, and both account for total weight percent and are 0.05-0.10%, and nucleator is sorbyl alcohol, inorganic salt, organic salt, and it is 0.05-0.3% that nucleator accounts for total weight percent.

(2) drop in two-way stretch film-making machine by above-mentioned particle, after setting, thickness is less than or equal to 40um, then makes polyethylene film.

5. preparation method according to claim 3, is characterized in that, described nucleator is organic calcium salt.