JPH0680130B2 - Polymer blend - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polymer formulations as surface layers or coatings. More specifically, the present invention is coextruded on one or both sides of a packaging film to provide longitudinal and transverse (fo)
rm) and fill film packaging with surprisingly good hot tack and heat sealability (he)
It relates to polymer formulations capable of providing sealing surface (s) exhibiting at sealability.

The present invention represents a unique problem associated with vertical and horizontal sealing and filled packaging materials. Packaging can be accomplished by filling food items, chemical solutions, etc. from a horizontal position where the item is inserted into the package from the open side. It is often desirable to fill the packaging from a vertical position. This is often desirable when the bag is filled with a free-flowing composition or several items where the horizontal filling process is difficult.

Shaped and filled film packaging require good "heat tack" and it is desirable to have a low heat seal onset temperature and a wide seal temperature range. Heat tack can be defined as the bond strength acting between two pieces of polymer film immediately after they are heated and brought together, where the polymer is in a semi-molten / solidified state. . Vertical and filled film packaging processes require simultaneous sealing of the bottom seam of the package and package filling while the package is in a vertical position. Thus, the package is sealed by the application of heat, and the seal must be strong enough to contain the hot filled material so that the material or product does not fall out of the bottom seal. Not only does the weight of the material or product contribute to eliminating this tendency to the bottom seal, but in addition the pressure of the air used to help transport the product can exert additional pressure on the seal.

In addition to good heat tack and a low and wide heat seal onset temperature range, 1) low coefficient of friction, 2) high seal strength, and 3) good compatibility with other packaging materials are also important.

Films for portrait and landscape and filled packages have traditionally suffered from one or more of these desired properties. Sealing layers such as the commonly used propylene-ethylene copolymers melt at elevated temperatures compared to the main packaging film; i.e. they have a high and narrow sealing temperature range. In this case, packaging rates are slower than desired, energy consumption is high, and damage to the main packaging can occur if the heat seal temperature is not adjusted very closely. An alternative sealing material is a metal salt of ethylene acrylic acid copolymer, which has a poor coefficient of friction and tends to stick on the mandrel created during the molding of the package. In addition, these materials have poor compatibility with other materials in packaging and can be easily recovered (reclaimabili
ty) is scarce.

Surprisingly, the known sealing coatings
Polymer formulations have been found which overcome the disadvantages of g) and exhibit all the desired properties of a good seal coat.
The formulations of the present invention may be advantageously used for vertical and filled film packaging (as well as horizontal). This formulation is low,
It has a wide seal temperature range and a low coefficient of friction combination not found in seal layer compositions. This formulation has good compatibility with other materials, especially polypropylene, and has excellent seal strength. Most importantly and surprisingly, this formulation exhibits good thermal tack over a wide, wide heat seal onset temperature range previously unattainable with other polymer formulations.

For example, U.S. Pat. No. 4,230,767 discloses packaging materials having heat seal packaging properties which consist of blends of propylene-ethylene copolymers with various other propylene olefin copolymers. The propylene ethylene copolymer in this patent has an ethylene content below 0.5% by weight. Neither of these patents discloses film packaging suitable for vertical and horizontal and filling methods, which shows good thermal tack. Also, this patent does not disclose films for vertical and horizontal and filled packages having a low and wide heat seal initiation temperature range.

Surprisingly, the butene-propylene copolymer is low,
It is possible to provide the layer with a broad seal onset temperature and, surprisingly, age at elevated temperature (tested at 55 ° C, 1,7 and 14 days) and a minimum of 3.5% (0 of the above patent). .
Propylene-with an ethylene content (rather than 5%)
Blends of ethylene copolymers not only have excellent thermal tack properties, but are conventionally achieved with any of the other blends of polymers that represent low heat to the typical blends or films of the above patents and films. It was found to produce a seal coat that also had a heat tack result that was not present. In order to produce a seal coat having excellent heat tackiness, as well as a low and wide heat seal initiation temperature range, a specific range of ethylene content of 3.5-10% in the propylene-ethylene copolymer has a butylene-propylene copolymer content. It has been found to be critical for polymer blends of polymers.

Also, propylene-which is not aged at these elevated temperatures
Blends of ethylene copolymers are capable of producing excellent heat tack to films at ethylene contents below 2.5% and a seal coat having a low, wide heat seal range, as can be seen from the tables herein. Was found.

This seal coating is polypropylene material polymer,
It can be used on films of copolymers or polypropylene blends.

FIG. 1 shows butene-1-propylene and propylene-coated on one side of a polypropylene substrate (PP).
It is an appearance of two layers of an ethylene copolymer film structure (BP / PE).

FIG. 2 is the appearance of a tri-layer (BP / PE) of butene-1-propylene and propylene-ethylene copolymer film structure coated on both sides of a polypropylene substrate (PP).

A heat tack and heat seal initiation temperature test was first conducted using a butene-1-propylene copolymer (R2598) having the properties outlined in Table 1 below.

Table 1-Butene-1-propylene Copolymer (R2598) Properties C ₃ =, wt% by NMR 19.8 Melt Index, g / 10 min 0.38 ASTM D1238Condition “E” Molecular Weight, Mw 716,000 Mn 145,000 Mz 2,140,000 Melting Point (Second Heating) ° C (DSC, @ 10 ° C / min) 75.5 Blend this butene-propylene copolymer with different propylene-based polymers and propylene-ethylene copolymers, then cast this with a homopolymer polypropylene substrate. (Cast) Film was coextruded. The coating is coextruded on polypropylene, which may or may not be biaxially oriented. Sealing and heat bond tests are performed with the desired dwel
l) and pressure to cure the heat sealer. Two seconds and 20 psi were used. Air pressure was preset to an inch of water through the regulator and column, a flat specimen approximately 3 inches long by 3 inches was placed on the shovel, and one end of the tube was sealed with adhesive tape. The shovel was brought to the jaws of the heat sealer so that the distance between the end of the seal rod and the end of the shovel was 2.5 cm, and the timer was set. Observe the distance of the opening in the sealing area immediately after opening the chin, then reduce the pressure and re-set, and set the maximum pressure (heat adhesive) to equal or less than the 0.3 cm seal opening. Subsequent steps were performed until obtained.

Example 1 Table 2 shows butene blended with a homopolymer polypropylene.
-1-Propylene copolymer and various propylene-ethylene
Heat seal initiation temperature (HSIT) and thermal adhesion strength of ren copolymer
And as a standard Arco 100% Propylene Ethyl
Len Commercial Copolymer Dypro431 Shows the thing. Manufactured,
And when it's aged at room temperature for at least 24 hours,
The heat tack strength of Rum was tested. Coating packaging film
Commercial propylene-ethylene copolymers used in
Arco Dypro 431 Was used as a standard. Transparency
In an amount of 0.2% by weight to improve
Was added.

As can be seen from Table 2, 60% butene-1-propylene and 40% propylene-ethylene W431 copolymer (composition N
The o.3) formulation gave the best heat tack as well as the lowest heat seal onset temperature. Composition No. 1 was a commercially used propylene-ethylene copolymer and contained 0% butene-1-propylene copolymer and 100% propylene-ethylene W431 copolymer. As can be seen, the heat seal initiation temperature was extremely high at 270 ° F and the heat tack strength was not acceptable up to 280 ° F.

In contrast, the preferred composition, No. 3, has a heat seal initiation temperature below about 170 ° F, good heat tack at 12.5 inches at 190 ° F and excellent heat tack in the range of 200-290 ° F. Expressed strength. 40% W431 at 12.5 inches, even at 190 ° F
The hot tack strength of the formulation was quite acceptable.

Composition No. 8 illustrates the use of WRS6-135 polymer at 2.5 wt% ethylene, with a heat seal initiation temperature of 195 ° F and excellent heat tack strength (210-290 ° F range). 15 ")
Occurred. In contrast, compositions Nos. 4 and 5 (3.2 wt% ethylene at melt flows 2 and 10, respectively) had high heat seal initiation temperatures (190 and 200, respectively) and only 210 ° F and 220 ° F, respectively. Then, it was shown that the heat adhesive strength that was allowable was exceeded.

Example 2 Table 3 shows butene-1 blended with the homopolymer propylene.
-Heat seal initiation temperature (HSIT) and heat tack strength of propylene copolymers and various propylene-ethylene copolymers,
And as standard the product of Dypro 431, a 100% propylene-ethylene commercial copolymer from Arco. The copolymers were aged at 55 ° C. for 1,7 and 14 days, respectively, and the heat tack ratio was measured at each of these aging times for each copolymer. Dy, a commercial propylene-ethylene copolymer used in coating packaging films
pro431 was used as a standard. 0 to improve transparency.
The millad was added in an amount of 2% by weight.

As can be seen from Table 3, composition # 6 containing 2.5% ethylene exhibits excellent thermal cohesive strength during manufacture, but
After aging at 55 ° C for only one day, it showed only normal thermal tack strength. The heat tack strength became poor after 7 days.

In contrast, composition # 5 containing 3.5% ethylene had good heat even after 7 days of aging and in the temperature range of 99-138 ° C and 115-138 ° C for 1 day and 7 days, respectively. It showed tackiness.

It is desirable to add film processing aids and end use enhancers to the film. These can be added without interfering with the heat tack and heat seal onset temperature range results.

[Brief description of drawings]

FIG. 1 is a two-layer appearance of a butene-1-propylene and propylene-ethylene copolymer film structure coated on one side of a polypropylene substrate. FIG. 2 is the appearance of the three layers of butene-1-propylene and propylene-ethylene copolymer film structure coated on both sides of a polypropylene substrate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-54-60348 (JP, A) JP-A-61-106648 (JP, A) JP-A-50-14741 (JP, A) JP-A-54- 52157 (JP, A) JP 55-91665 (JP, A) JP 59-207952 (JP, A) JP 61-108646 (JP, A) JP 61-108647 (JP, A) US Patent 4230767 (US, A)

Claims (4)

[Claims] 1. A copolymer of butene-1 and propylene having a propylene content of about 12 to about 30% by weight, and about 2.5 to.
A copolymer of propylene and ethylene having an ethylene content of about 10% by weight, wherein the butene-1-propylene copolymer and the propylene-ethylene copolymer are about 40: 60-
A polymer blend formulated in a weight ratio of about 75:25. 2. The propylene content of the copolymer of butene-1 and propylene is about 15 to 25% by weight, and the ethylene content of the copolymer of propylene and ethylene is about 5 to about 7% by weight. %, And the butene-1-propylene copolymer and the propylene-ethylene copolymer are about 60:40 to about 7%.
A polymer blend according to claim 1 formulated in a weight ratio of 0:30. 3. The butene-1-propylene copolymer has a propylene content of about 20% by weight, the propylene-ethylene copolymer has an ethylene content of about 6% by weight, and the butene. The polymer blend of claim 1 wherein the -1-propylene copolymer and the propylene-ethylene copolymer are blended in a weight ratio of about 65:35. 4. The method of claim 1 wherein said polymer blend has an acceptable heat tack range of about 200 to about 290 ° F. and a heat seal initiation temperature of about 170 to about 200 ° F. Polymer blend.