JP2887747B2 - Film suitable for food packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film suitable for food packaging.

[0002]

Background of the Invention Blends of maleic anhydride graft copolymers and polyolefins have a wide range of applications, including use as ingredients in coating food packaging films and pipes. Methods for grafting ethylenically unsaturated monomers such as maleic anhydride onto olefinic polymers are well documented by those skilled in the art. Typically, the method involves reacting maleic anhydride with a molten olefinic polymer under high shear conditions. A wide range of mixing devices are generally described as suitable. However, the only practical example involving the use of a multiple screw extruder is U.S. Pat. 4684576, found in Example 1. The examples essentially create important conditions that have been found to be necessary to produce a grafted product suitable for food packaging films requiring the absence of odor, low granularity and colors other than yellow. Does not disclose or suggest.

[0003] The products obtained from conventional extrusion methods are not suitable for use in food packaging films for three main reasons. 1) Smell. The incorporation of monomers into the graft copolymer in conventional methods is very small. Generally, the graft copolymer contains less than 0.50% by weight of maleic anhydride. These copolymers then contain significant amounts of residual monomers and other impurities that give the film a very unpleasant odor. These films are therefore unacceptable for use as food packaging materials.

2) High particulate matter content. Granules defined as small spherical masses separated from the polymer itself having a diameter of 5 to 15 mils have long been found to adversely affect the clarity and gloss of extruded films. Ho
wells and Benbow, "Flow Defec."
ts in Polymer Melts ”, Tran
s. J. Plast. Inst. 30 (1962) 24
0-253 concludes that the formation of particulates is due to intramolecular entanglement during the extrusion process, and this entanglement can be reduced but not eliminated by shearing. Generally, the higher the degree of chain entanglement, the greater the amount of particulates in the extruded film, and thus the more cloudy the film. Films made of conventional graft copolymers have high levels of particulates and are therefore undesirable for food packaging applications.

3) Yellow. Films made from conventional graft copolymers also have the undesirable feature of yellow discoloration that is aesthetically unacceptable to the consumer and is therefore not practical for food packaging applications. It would be advantageous to consider a method of producing a maleic anhydride graft copolymer that when blended with a polyolefin would make the film suitable for use as a food packaging material. In particular, it is desirable to produce a graft copolymer containing more than 0.50% by weight of incorporated maleic anhydride with a low yellow index, which when blended with a polyolefin, results in a low particulate content of the film.

[0006]

The present inventors have succeeded in producing a maleic anhydride graft copolymer satisfying the above requirements by the following method. (A) feeding the polymer, maleic anhydride and free radical initiator to the multiple screw extruder; (b) melting the polymer by heating and shearing in the extruder; and (c) Then mixing the molten polymer and maleic anhydride in an extruder for a time sufficient for at least a portion of the maleic anhydride to graft to the molten polymer, wherein the adding of the maleic anhydride in step (a) This is preceded by step (b) and is characterized by injecting maleic anhydride and a free-radical initiator into the part of the multi-screw extruder which is further pressurized and filled with the molten polymer. The maleic anhydride and free radical initiator are preferably mixed in a solvent system prior to injection into the extruder. Evaporation of the volatiles of the graft copolymer preferably takes place in one or more vacuum sections of the extruder.

[0007] The present invention comprises a graft copolymer as one essential component.
Of a multilayer having at least one layer of a blend
A food packaging film, wherein the graft copolymer is 1
It has a yellow index of less than 0.0 and has a maleic anhydride model.
Nomer equivalent content of 0.5 to 2 per graft copolymer
% By weight and (a) multiples with positive and negative transport elements
Supply backbone polymer to double screw extruder
Heating the polymer in an extruder and subjecting it to shearing action.
(B) filling with the molten polymer
Maleic anhydride and free radical initiator in the zone being pressurized
(C) the molten polymer and maleic anhydride
And graft copolymerization by mixing
And a film for packaging food .

[0008] The present invention is also a multilayer coextruded film used to package foods containing at least two layers, wherein at least one layer comprises: (a) about 1.5 to 75.0% by weight of 10. A graft copolymer having a yellow index measured by ASTM D-1925 of less than 0 (the graft copolymer comprises a reaction product of maleic anhydride and a backbone polymer;
5 to 2.0% by weight of maleic anhydride) and (b)
25.0 to 98.5% by weight of a blend of polyolefins.

FIG. 1 is a schematic diagram of a preferred apparatus for grafting maleic anhydride to a polymer. The graft copolymer used in the present invention has an A of less than 10 and 11, respectively.
STM D-1925-70 and ASTM E-313
Has a yellow index as measured by -73, and has particular applicability as a component in multilayer extruded films;
It is particularly useful as a packaging material for food.

The graft copolymers of the present invention are prepared in a multiple screw extruder comprising positive and negative transport screw elements and kneading / mixing plates with projections, paddles or blocks. In general, the positive transport screw element comprises a zone from the beginning of the extruder (where the polymer, maleic anhydride and initiator are first received and mixed) to the zone after the extruder (where the polymer volatiles are removed). And discharged from the extruder) to carry the polymer / maleic anhydride stream. The negative transport screw element tends to direct the flow from the later zone to the first zone. It is the negative transport screw element that serves to back up the polymer or fill the area of the extruder located upstream of them. In essence, any multiple screw extruder may be used that includes a screw element having means similar to those described herein. The screws will probably rotate counter to each other.

A representative example of a multiple screw extruder suitable for use in the present invention is a fully intermeshing, simultaneously rotating twin screw extruder shown schematically in FIG. The term "co-rotation" means that all screw elements rotate in the same direction at the same rotational speed. Although the invention is described by this figure, it will be appreciated that any multiple screw extruder may be used, including means similar to those described above.

The drive unit 4 comprises a positive transport element 6, a negative transport element 8 and a mixing / kneading paddle or block 1.
8 is rotated in the barrel 2 of the extruder. The positive transport element 6 is generally the extruder barrel 2 from left to right in FIG.
Carry the material within. The negative transport element 8 temporarily delays the movement of the material, backs up the material and fills a part of the extruder barrel 2 upstream of the negative transport element 8. The negative transport element 8 divides the extruder barrel 2 into four separation zones 10, 12, 14, 16. The first zone 10 includes a positive transport element 6 and a mixing type element 18 for receiving and mixing the polymer, maleic anhydride and free radical initiator. The second zone contains the positive transport element 6 and further mixes the polymer by shearing while effecting the grafting. If additional mixing or residence time is desired, negative transport 8 or mixing / kneading paddle 18
Can replace some of the positive transport elements 6 in the zone 12 of the extruder. Third zone 14 and fourth zone 1
6 includes a positive transport element 6 and is provided for evaporating the volatiles of the polymer as described more fully below.

The basic or backbone polymer is fed in the form of pellets from a feed hopper 20 to a feed metering conveyor 22 and then to the feed inlet 2 of the extruder barrel 2.
4 is supplied. The feed inlet 24 is located in the extruder barrel 2 near the beginning of the first zone 10. Backbone polymers include, but are not limited to, (i)
Polyolefins such as polypropylene, poly (4-methylpentene), high-density polyethylene "HDPE" (0.
Density of ^{940g / cm 3 ~0.965g / cm 3} ), low density polyethylene "LDPE", the main distinction of these polymers, are well known to those skilled in the art, U.S. Pat. No. 4,327,009 to herein are incorporated by reference (Ii) linear low-density polyethylene “LLDPE” fully described in
(0.870 g / cm ³ density of ~0.939g / cm ³⁾ or ethylene and linear copolymers of α- Ofin example 1-octene having from about 3 to about 10 carbon atoms,
(Iii) copolymers of ethylene and carbon monoxide and (iv) those selected from the group consisting of, but not limited to, acrylic acid, methacrylic acid, alkyl acrylates (eg, ethyl acrylate, butyl acrylate, etc.) and vinyl acetate And ethylenically unsaturated carboxylic acids and derivatives.

The barrel 2 of the extruder is preferably heated by a clamped electrical element or preferably cooled by circulating water to control the temperature of the polymer. The temperature inside each of the four zones 10, 12, 14, 16 is independently controlled to obtain the desired temperature profile, even when processing polymers having different melting properties.

The maleic anhydride and free radical initiator are preferably injected into the extruder barrel 2 into the polymer-filled, under-pressure portion of the extruder barrel 2 at the mixing element 18 at the end of the first zone 10. As used herein, when used with respect to an extruder, the term "polymer-filled" refers to a portion of the flight and area of the screw where substantially all voids are essentially filled with polymer. I say Further, the term "pressurized portion", when used in reference to an extruder, means that substantially no gaseous voids are present and any solvent pumped to the region is substantially above its evaporation point It relates to an area that is filled with a polymer so as to be sealed to the extent that it is kept under and that is under pressure from the polymer stream. Negative transport element 8 at the end of the first zone 10
Keeps the mixing element 18 filled with polymer and improves mixing.

Suitable free radical initiators include, but are not limited to, alkyl peroxides and dialkyls such as tertiary-
Butyl peroctoate (2-ethylhexanoate)
Or 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3. Initiators with high stability are preferred.

The maleic anhydride is preferably mixed in a non-reactive solvent such as ketone, benzene, alkyl acetate or chlorinated benzene and stored in the maleic anhydride feed tank 30. Maleic anhydride can be dissolved in the solvent to its saturation level. In addition, the free radical initiator can be mixed with maleic anhydride during storage, or separately injected into the barrel 2 of the extruder. Maleic anhydride and solvent solution are pumped from storage tank 30 by metering pump 32 and injected into first zone 10 through injection nozzle 34. If the free radical initiator is added separately or if additional initiator is needed, the free radical initiator is stored in the solvent solution in the second storage tank 40 and the second injection nozzle 44 It is pumped by a second metering pump 42 to be injected into the first zone 10. The amount of initiator used does not seem to be strict, and
/. 015 to about 1 /. A maleic anhydride to initiator ratio of 1 (by weight) was found to be satisfactory, in which 1 /. 0
25/1 /. A ratio of 035 is preferred.

The temperature of the polymer in the first zone 10 is usually lower than its melting point, and the temperature of the polymer in the second zone 12 is
It must be high enough to keep the polymer in its molten state. Independent temperature control for each zone is desirable because the polymer generally experiences an increase in viscosity as the maleic anhydride is grafted onto the polymer. Higher melting temperatures, eg, above 250 ° C., require more stable initiators than those described above. 85-
The polymer having a melting point of 190 ° C. is Lupersol.
Works well when 130 is used as an initiator.

The pressure in the first zone 10 is not critical. However, the area 34 where maleic anhydride is injected into the extruder must be maintained at a pressure above the maleic anhydride evaporation pressure, preferably about 50-100 psig. The pressure in the third zone 14 and the fourth zone 16 is
Must be low enough to remove solvents and unreacted maleic anhydride. A vacuum source 50 is provided to reduce the pressure in the third and fourth zones 14 and 16,
A vacuum of 29.9 inches (mercury) was shown to be sufficient to remove most of the unreacted maleic anhydride.

The temperature of the graft copolymer during devolatilization is preferably between about 160 and 3 to aid in devolatilization.
Keep between 00 ° C. High temperatures give low volatile levels, but lead to high particulate levels. Lower temperatures lead to higher volatile levels or more work input to remove volatiles,
This results in low particulate levels. Temperatures of about 180-260 ° C are preferred to provide the best balance between devolatilization and particulate levels.

The graft copolymer exits the extruder barrel 2 through a die face 60 which produces a strand of graft copolymer. The polymer strands are then sent to a strand chopper 70 to produce polymer pellets for use in other ways. Alternatively,
An underwater pelletizer can optionally be used in place of the strand chopper 70. Any of these technologies
It is generally well known to those skilled in the art.

A multiple screw extruder particularly suitable for the present invention is a commercially available Werner-Pfleiderer.
It is a ZSK-53 / 5L simultaneous rotation twin screw extruder. The extruder can graft maleic anhydride to the polymer backbone at a rate of 40 pounds to 160 pounds per hour without significant change in percent conversion. Even production rates of up to a maximum of this device (about 300 pounds per hour) can be obtained. The backbone is preferably quantitatively fed into the polymer feed inlet at a rate sufficiently low to run out of the extruder at the operating speed prior to the addition of maleic anhydride and free radical initiator. The average residence time in the extruder is about 140 seconds at 40 pounds per hour to about 4 seconds at a polymer rate of 160 pounds per hour.
It lasts 5 seconds. Larger diameter similarly equipped extruders also give similar products at a higher rate.

The method and apparatus described above can be used to graft maleic anhydride to a polymer to produce a graft copolymer having up to about 2% by weight of maleic anhydride.
The percentage of maleic anhydride loading generally relates to the ratio of maleic anhydride to polymer to about the maximum loading level, and is about 2%. Preferred products are generally from about 0.3 to about 1.5% by weight of maleic anhydride, most preferably 0.5% by weight.
0% by weight or more of maleic anhydride,
Most preferred is at least 5% by weight.

A 75% conversion of the maleic anhydride grafted to the feed maleic anhydride is achieved for linear low density polyethylene, and a low percentage conversion is generally obtained for high density polyethylene.

The graft copolymers produced from the process of the present invention have improved color properties and improved particulate properties when produced into films. In particular, AS
The yellow index of the polymers of the present invention as measured by TMD-1925-70 is less than about 10.0, usually about 8.7.
5 and generally less than about 11.0 as measured by ASTM E-313-73, usually about 8.7.
Lower than 5. Additionally, the whiteness index as measured by ASTM E-313-73 is greater than 45.0. In addition, the blends of the present invention, comprising a polyolefin and a graft copolymer when processed into a film, may be from 5 mil to 1 mil.
10 mils of 1.6 mil film with 5 mil particle diameter size
It is characterized by a particle count of less than about 3000 per 00 square inches. These films have a very glossy appearance and are suitable for use as multi-layer co-extruded or laminated food packaging materials.

The polyolefin with which the graft copolymer of the present invention is blended is an ethylene homopolymer containing LDPE and HDPE. Furthermore, suitable polyolefins to produce films, polyolefins, poly (4-methylpentene) and ethylene and C ₃ -C ₁₀ alpha-olefins for example LLDPE, a copolymer of polypropylene and 1-butene, ethylene and C ₄ -C ₈ copolymers of diolefins such as butadiene and ethylene and ethylenically unsaturated carboxylic acids or derivatives such as vinyl acetate, acrylic acid, methacrylic acid, ethyl acrylate, butyl acrylate, methyl methacrylate and methyl acrylate and Includes copolymers of ethylene and carbon monoxide. The ratio of graft copolymer to polyolefin used in the blend generally ranges from about 1.5: 98.5 to about 75: 2.
5 (weight), preferably about 2.5: 97.5 to about 35:
65 (weight), most preferably from about 5.0: 95 to about 2
5:75 (weight).

The graft copolymer and polyolefin are
Blending can be accomplished by methods known to those skilled in the art, for example, using a blender, mixer, kneader, roller, extruder, and the like. Similarly, the formation of multilayer films from these blends can be accomplished by techniques such as cast film, blown film, co-extrusion blow molding, co-extruded sheet manufacturing, lamination, or techniques available to those skilled in the art. Layers of these multilayer films (other than a layer composed of a blend of a graft copolymer and a polyolefin) include polyamide (eg, nylon), ethylene-vinyl alcohol copolymer, and polyolefin (eg, polypropylene,
Polyethylene, etc.), polyesters, polycarbonates and synthetic resins such as poly (vinylidene chloride), cellulose and their derivatives, and metals.

The following Examples 1-3 and some of Examples 8-12 provide details of the preparation and use of the preferred graft copolymers by the method of the present invention. Comparative Examples 4 to 7, 1 below
Some of 3 and 8-12 are not prior art. They show the surprising features of the present invention. In Examples and Comparative Examples, “melt fluidity” refers to ASTM D-1.
238, Standard Designation
The melt flow index was measured using 190 / 10.0 (condition N). Yellow index (A) is ASTM D-192
Determined using 5-70. White index and yellow index (B)
Was determined using ASTME-313-73.

Example 1 Melt Index of 6 dg / min and 0.919 g / c
c having a density of "DOWLEX (Dow C
chemical Company trademark) LLDPE
2035 ”(DOWLEX LLDPE 2035
Octene / ethylene copolymer) is commercially available under the following conditions.
erner-Pfleiderer ZSK-53 / 5
It was fed to an L co-rotating twin screw extruder. Zone 1 2 3 4 Barrel temperature (° C.) 215 228 233 235 Melting temperature (° C.) 135 200 210 240 Screw speed 200 rpm Polymer speed 150 lb / hr

The maleic anhydride / methyl ethyl ketone / LUPERSOL (2,5-
A mixture of 130 dimethyl-2,5-di (tert-butylperoxy) hexine-3) was extruded through a Werner-Pfleiderer injection nozzle by a positive displacement metering pump at a rate of 2.24 pounds per hour. Note supplied. The injection nozzle is located just upstream of a series of kneading blocks or mixing type elements supported by a negative transport element, which extrudes from a point upstream of the injection nozzle to a negative transport screw element. The vessel was filled with the polymer and pressurized. A vacuum of 29 inches of mercury was maintained in zones 3 and 4 to evaporate the volatiles of the grafted polymer. The graft copolymer is
The formulation of maleic anhydride at 0.55% by weight of the grafted polymer is shown.

Example 2 Melt index of 10 dg / min and 0.962 g / min
"DOWHDPE 10062" having a density of cc
Was supplied to the extruder of Example 1 under the following conditions. Zone 1 2 3 4 Barrel temperature (° C.) 170 230 220 220 220 Screw speed 200 rpm Polymer speed 150 lb / hr

A solution of 45/55 / 0.032 (methyl ethyl ketone / maleic anhydride / LUPERSOL 130) was fed through the injection nozzle at a rate of 5.9 lb / h. The vacuum level in Zones 3 and 4 was 29 inches of mercury. The product contained 1.15% maleic anhydride. This product is then 11.5 / 88.5 (88.
"DOWLEX (DowChemi), a linear low density polyethylene having a melt index of 6 dg / min and a density of 0.919 g / cc at a ratio of 5% LLDPE).
cal Company trademark) L LLDPE 203
5 "(DOWLEX LLDPE 2035 is an octene / ethylene copolymer), melt blended in an extruder, and then co-extruded as an adhesive (intermediate) layer of a three-layer film comprising high density polyethylene and nylon. Was. The resulting film, when bagged, has excellent structural integrity and is suitable for heating the contained food product in a microwave oven.

Example 3 "DOWH" having a melt index of 10 dg / min
A high-density ethylene homopolymer commercially available as "DPE 10062" was fed to the extruder of Example 1 under the following conditions. Zone 1 2 3 4 Barrel temperature (° C.) 102 201 201 221 Screw speed 300 rpm Polymer speed 200 lb / hr

Methyl ethyl ketone, maleic anhydride and LUPERSOL 130 were converted to 3.4, 3.4, respectively.
And 0.10 lb / hr fed through the injection nozzle. The injection nozzle was located just upstream of a series of kneading blocks or mixing type elements supported by a negative transport element, which filled the entire injection area with polymer and pressurized. The vacuum level in Zones 3 and 4 was 29 inches of mercury. The product contained 1.02% formulated maleic anhydride and showed a 63.0% conversion of the feed maleic anhydride to the formulated maleic anhydride.

The obtained graft copolymer exhibited the following properties. Melt fluidity 9.8 Whiteness index 49.94 Yellowness index (A) 8.53 Yellowness index (B) 8.69

(Comparative) Examples 4-6 These examples demonstrate that high yellow index and low white index are obtained when maleic anhydride and initiator are not injected into the polymer filled portion of the extruder. Prove it. In the polymer feed section of the extruder of Example 1, Dow H
DPE 10062, maleic anhydride (MAH) and L
UPERSOL 130 was added. The extruder was operated under the following conditions.

The implementation Example 4 5 6 Barrel Temperature (° C.) 181 181 184 Zone 1 199 200 203 Zone 2 204 203 201 Zone 3 200 194 232 Zone 4 200 250 Screw speed (rpm) polymer feed rate (lb / hr) 100 100 200 MAH feed rate (lb / hr) 1.9 1.9 3.8 LUPERSOL feed rate (lb / hr) 0.1 0.25 0.1 Zones 3 and 4 vacuum level is 29.88 inches of mercury Met. The injection nozzle was arranged as in Example 3 above. The resulting graft copolymer exhibited the properties summarized in Table I.

[0038] Table I implementation Example 4 5 6 melt flow 5.2 0.9 8.2 MAH formulation (wt%) 0.98 1.20 1.11 MAH Conversion (wt%) 51.5 53.7 58.4 White index 37.12 -9.56 42.36 Yellow index (A) 12.78 28.22 1.13 Yellow index (B) 13.34 30.31 11.59

(Comparative) Example 7 This example illustrates the importance of the design of the extruder screw element. A twin screw extruder similar to that of Example 1 was used, except that the negative transport element was replaced with a positive transport element. (As a result, the extruder was not filled with polymer at the point of injection and was not pressurized.) A vacuum of 29 inches of mercury was maintained in zones 3 and 4 to evaporate the volatiles of the graft copolymer. I let it. Extruder Zone 2
Inside, MAH, LUPERSOL130 and methyl ethyl ketone (MEK) were added. The operating conditions of the extruder were as follows.

Zone 1 2 3 4 Barrel temperature (° C.) 85 119 192 192 Screw speed 200 rpm 300 MAH supply speed 3.7 lb / hour MEK supply speed 3.7 lb / hour LUPERSOL supply speed 0.11 lb / hour

The properties of the obtained graft copolymer were as follows. Table 1 Melt flowability 15.4 MAH formulation (% by weight) 17.3 MAH conversion (% by weight) 0.32 White index 56.84 Yellow index (A) 6.28 Yellow index (B) 7.10 The graft copolymer had an unacceptably strong and unpleasant odor due to residual monomers.

Examples 8-12 158 g of the product obtained in Example 3 above and Comparative Examples 4-7 were weighed at 24: 1 length / diameter ratio and in Zone 1 at 325.F, Zones 2 and 3. Using a three zone, one inch single screw extruder with a barrel temperature of 375 ° F. at DOWLEX (Dow Chemical
l Company trademark) LLDPE4035 (DO
WLEX LLDPE 4035 is a linear low density polyethylene (LLDPE) having a melt index of 5.5 dg / min and a density of 0.919 g / cc) 12
It was melt blended with 42 g. The resulting pellets are then passed in zones 1 and 2 at 300.F and 375.F, respectively.
In addition, die zones 2 and 3 were fed to a 3/4 inch Killion single screw blown film extruder having a barrel temperature of 375 ° F. A 3 inch frost line was maintained in each case. The extruded monolayer film had a final maleic anhydride comonomer content of 0.13% by weight.

Example 3 and Comparative Examples 4 to 7 (C4 to
The 1.6 inch thick 8 inch wide films of each of 7) were placed in a light box. 1.5 inch x 0.5
An inch template was placed on the film. The number of granules having a diameter of 5 to 15 mils in the template area under a 10x lamp (Art Specialty Co, Illinois Chicago) was then determined. The results, shown below, are expressed in units of granules per 1000 square inches of 1.6 mil film.

Example 3 C4 C5 C6 C7 2773 8107 15819 4053 ** Film could not be made with a blend amount that provided a maleic anhydride content suitable for adhesion performance.

(Comparative) Example 13 In this example, when the maleic anhydride (MAH) graft monomer was premixed and supplied to the extruder (Sample A), and simultaneously supplied (Sample B) ) Or when fed to a conventional feed (Sample C), showing that lower conversions are obtained than aspects of the present invention (particularly described in Examples 1-3).

Sample A A mixture of maleic anhydride and dicumyl peroxide (10: 1 each by weight) was fed into the extruder of Example 1. The mixture was dissolved in acetone and sprayed onto high density polyethylene (HDPE) pellets. The acetone was evaporated and the coated pellets were fed as concentrate along with the uncoated pellets into the extruder suction section.
A mixture of 7.8% polymer / 2% maleic anhydride / 0.2% dicumyl peroxide was fed. Devolatization was performed in zone 3. The data is shown in Table II.

Sample B Linear low density polyethylene having a 25 melt index (L
The maleic anhydride concentrate in LDPE) was added to Bunbury.
Made in a mixer and then granulated. The concentrate is 10%
Maleic anhydride. A dry blend of this concentrate and dicumyl peroxide is made and the concentrate is fed to the extruder of Example 1 along with untreated polyethylene to give 97.9.
The feed ratio was 1% polymer / 1.9% maleic anhydride / 0.19% dicumyl peroxide. The data is shown in Table II. Furthermore, these copolymers had an unacceptable odor for use as a food packaging component.

Table II PHR MAH PHR Peroxide % grafted MAH % conversion polymer sample 2.2 0.2 0.60 27.3 HDPE A 1.9 0.2 0.52 27.4 LDPE B PHR = Polymer 100 Pounds per pound

Sample C The extruder of Example 1 was used except that 59/3/3
Maleic anhydride (MA) dissolved in methyl ethyl ketone (MEK) at a weight ratio of 8 (MAH / peroxide / MEK)
H) and attach the peroxide to a plate attached with a metal plug commonly used to form a twin screw-shaped profile to serve as part of the barrel, except for some of the air in the extruder. Into the zone 2 via a closed tube. The polymer was fed into the extruder suction. At the point where the solution was introduced, the polymer melted. Solvents and unreacted monomers were devolatilized in zones 3 and 4 in vacuo. Appropriate data is shown in Table III. It should be noted that these copolymers had an unacceptable odor for use as a food packaging component.

[0050] Table III Sample C grafted maleic anhydride according to the method of the PHR MAH PHR peroxides% grafted MAH% conversion Polymer ^{2 0.1 2 0.16 8 HDPE 2 0.1} 3 0.11 5.5 ^{HDPE 2 0.1 2 0.58 29 LLDPE 2} 0.1 2 0.44 22 LLDPE 2 0.1 2 0.37 18.5 LLDPE 2 0.1 2 0.82 41 LLDPE 2 0.1 2 0. 4824 LLDPE PHR = pounds per 100 pounds of polymer ² dicumyl peroxide ³ t-butyl hydroperoxide

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a graft device.

[Description of Signs] 2 Extruder barrel 6 Positive transport element 8 Negative transport element

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 51/08 C08L 51/08 // C08F 255/02 C08F 255/02 283/00 283/00 C08G 67/02 C08G 67/02 (72) Inventor Gerald M. Lancaster 77541 Freeport Tarpon Ave, Texas, USA 303 P.O. Box 801 (56) References JP-A-55-128455 (JP, A) JP-A-56-60224 (JP, A) Kaikai 64-110 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 51/00-51/08 C08F 8/46 C08F 251/00-292/00

Claims (11)

(57) [Claims] 1. A graft copolymer as one essential component.
Multi-layer food package having at least one layer of a blend
A wearing film, wherein the graft copolymer is 10.0
Maleic anhydride monomer with lower yellow index
The converted content is 0.5 to 2% by weight based on the graft copolymer.
And (a) a multiple disk with positive and negative transport elements
Supply backbone polymer to Liu extruder and push
The polymer is heated in a dispenser and melted by shearing
And (b) being filled with the molten polymer and pressurized.
Maleic anhydride and free radical initiator into the zone where
(C) mixing the molten polymer with maleic anhydride
And obtained by graft copolymerization
Food packaging film. 2. The method according to claim 1, wherein the backbone polymer is a high-density polyethylene, a low-density polyethylene or ethylene and C ₃ -C ₁₀
The film according to claim 1, which is an olefinic polymer selected from the group consisting of olefins. 3. The film according to claim 1, wherein said backbone polymer is polypropylene or poly (4-methylpentene). 4. The backbone polymer is a copolymer of ethylene and a member selected from the group consisting of acrylic acid, methacrylic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, methyl acrylate and vinyl acetate. The film of claim 1. 5. The film of claim 1, wherein said backbone polymer is a copolymer of ethylene and either acrylic acid or carbon monoxide. 6. The film of claim 1, wherein said yellow index is less than 8.75. 7. The film of claim 1 wherein the whiteness index measured according to ASTM E-313-73 is greater than 45.0. 8. The method according to claim 1, wherein at least one layer comprises the graft copolymer.
Blend of 25.6 to 98.5% by weight of polyolefin
The film of claim 1 comprising: 9. The polyolefin is polyethylene, polypropylene, poly (4-methylpentene), a copolymer of ethylene and a C ₃ -C ₁₀ α-olefin, a copolymer of ethylene and a C ₄ -C ₈ diolefin, and 9. The film of claim 8, wherein the film is selected from the group consisting of ethylene and ethylenically unsaturated carboxylic acids or derivatives and copolymers of ethylene and carbon monoxide. 10. The film of claim 9 wherein said polyethylene is selected from the group consisting of low density polyethylene, high density polyethylene and linear low density polyethylene. 11. The blend of claim 10 wherein the number of particles of 5 mil to 15 mil particle size is 1.6 mil of film.
9. The film of claim 8, wherein less than 3000 per 00 square inches.