Ethylene-propylene copolymer low noise film additive

The invention pertains to an ethylene-propylene copolymer which when added to stretch film used in palletizing reduces the noise involved in use. The ethylene-propylene copolymer tackifier has a weight average molecular weight in the range of 7,000 to 18,000 and an ethylene content of 15-28 weight percent and results in polyethylene stretch films having both desirable cling and noise levels.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is concerned with blends of linear low density polyethylenes 
and ethylene propylene co-polymers and with low unwind noise, good cling, 
and commercially viable tackifier bleed-out rates and films made from 
them. 
2. Description of the Prior Art 
U.S. Pat. No. 4,430,457 discloses a stretch wrap film, but does not address 
the object of achieving low noise. 
U.S. Pat. No. 5,114,763 discloses a stretch film having a tackifying agent, 
a hydrogenated cycloaliphatic hydrocarbon, which is substantially 
different from the ethylene-propylene copolymers of this invention. 
U.S. Pat. No. 4,793,956 discloses a process for preparing a porous film or 
sheet having a filler. Good cling and low noise is not discussed as an 
object of the '956 patent. 
BRIEF SUMMARY OF THE INVENTION 
The invention relates to a linear low density polyethylene (LLDPE) stretch 
film used in palletizing and packaging. The invention is drawn to a film 
with low noise properties due to the particular characteristics of the 
blend of a LLDPE resin with a low molecular weight EP copolymer having a 
low percentage of ethylene, as a tackifying agent 
The invention provides blends, and films made therefrom, comprising a 
linear low density polyethylene containing by weight of the blend, between 
3% and 6% of an ethylene-propylene copolymer having an ethylene content of 
between 15% to 28% weight percent and weight average molecular weights of 
between 7289 and 60615, preferably between about 7000 to about 18,000. 
The invention provides for making stretch films with low noise, good cling, 
and commercially viable bleed-out rates of the tackifying agent 
An object of the invention is to provide a film with low noise when unwound 
during the stretch wrapper operation. 
A further object of the invention is to provide a film with low noise and 
good cling. 
A further object of the invention is to provide a film with low noise that 
has commercially viable bleed-out rate. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Tests were conducted using Eastoflex 1003, Eastoflex E1010, Uniroyal 
Trilene CP40-38, and Polytech PX4 as tackifying agents added to the LLDPE 
mixture. The results of these texts are summarized in Tables 1-4. 
Table 1 highlights the differences in the ethylene-propylene copolymer 
properties. The Eastman 1003 and the Uniroyal Trilene CP40-38 both have 
relatively low molecular weights of between 2100 and 2500. Both the 
Eastman 1003 and the Uniroyal Trilene CP40-38 have low polydespersity 
indices (Q) of between 2.9 and 5.6 compared to the other EP's tested. The 
weight average molecular weights of the Eastman 1003 and Uniroyal Trilene 
CP40-38 are lower than the PX-4 and E1010 tested. The ethylene contents of 
the Eastman 1003 and Uniroyal Trilene CP40-38 are between 20 to 28% and 
slightly overlap the Polytech PX-4. 
TABLE 1 
__________________________________________________________________________ 
EP PROPERTIES 
Molecular Weight by GPC 
Ethylene Content 
Melt Index 
Manufacturer 
Grade Mn Mw Q (%) by FTIR 
(g/10 min) 
__________________________________________________________________________ 
Eastman 
Eastoflex E1003 
2140 
11810 
5.52 
22 &gt;207 
Eastman Eastoflex E1010 2910 19960 6.86 9 
Polytech PX-4++ 2070 20620 9.96 28 
Uniroyal Trilene CP40-38 2470 7290 2.95 26 
__________________________________________________________________________ 
+EP extracted with hexane 
Table 2 highlights test formalities 1 through 4 which were run. Tests 1-4 
highlight monolayer films extruded on a laboratory blown film line. The 
base resin in all cases is a butene comonymer linear low density 
polyethylene. In Examples 1-4, the tackifying agents were used at or near 
their lowest effective levels. Cling was recorded at 200% stretch at 
different time intervals for 28 days. Exxan Parapol 1300 is a polybutene 
teckifier additive well known in the art. It is an effective tackifier. 
However, when used in moderate levels, it produces fairly high unwind 
noise. As shown in Example 1, the polybutene tackifier developed 
relatively high cling within three days, but this was accompanied with 
very high noise. Polytech PX-4 concentrate was used at a level of 10% in 
the film. The effective loading of ethylene-propylene copolymer was 5.5%. 
The film had very low noise. However, there was no measurable cling until 
14 days and there was not adequate cling until 28 days. Trilene CP40-38 
developed effective cling after 1 day of aging and had no noise. The 
Eastman E1003 also produced a film with no noise and effective cling after 
3 days of aging. 
TABLE 2 
______________________________________ 
TESTS 1-4: MONOLAYER FILMS 
Test # 1 2 3 4 
______________________________________ 
Composition (% by weight) 
butene LLDPE 96 90 95 95 
Exxon Parapol 1300 4 
PX-4 Concentrate* 10 
Trilene CP40-38 5 
Eastman E1003 5 
Test Results 
Noise High None None None 
Cling @ 1 day 60 0 175 90 
200% 3 days 185 0 175 120 
(grams) 7 days 280 0 200 130 
14 days 340 40 200 130 
28 days 260 100 206 110 
______________________________________ 
*-5.5% EP Copolymer in LLDPE 
Table 3 shows tests 5-8 comparing Eastman E1003 and Eastman E1010 at 4 and 
6% loadings. In tests 5 and 6, the Eastman E1003 developed an effective 
cling within a reasonable 7 days. Again, there was no loise. In tests 7 
and 8, the Eastman E 1010 at both 4 and 6% loadings also had no noise and 
no cling after 28 days of aging. The Eastman E1010 at both 4 and 6% 
loadings was found to be unacceptable due to very slow tack development. 
TABLE 3 
______________________________________ 
TESTS 5-8: MONOLAYER FILMS 
Test # 5 6 7 8 
______________________________________ 
Composition (% by weight) 
butene LLDPE 96 94 96 94 
Eastman E1003 4 6 
Eastman E1010 4 6 
Test Results 
Noise None None None None 
Cling @ 1 day 0 20 0 0 
200% 3 days 40 60 0 0 
(grams) 7 days 105 105 0 0 
14 days 145 145 0 0 
28 days 135 190 0 0 
______________________________________ 
Table 4 shows tests 9 and 10 which are coextruded films produced on a 
commercial scale blown film equipment. Both tests are ABA coextrusions 
(the composition of the two skin layers are identical). Test 9 is a 
polybutene tackified film containing a total of 3.5% polybutene. The 
polybutene is present in both the skin and the core layers. This film has 
good levels of cling at 135 grams but had very high noise (89 dB). The 
second film contains Eastman E1003 at a total loading of approximately 
4.5%. The E1003 was added in the form of a concentrate which was 40% 
ethylene-propylene copolymer in LLDPE. This film had very low noise at 70 
dB and good cling at 150 grams. 
TABLE 4 
______________________________________ 
TESTS 9 AND 10: COEXTRUDED FILMS 
Test # 9 10 
______________________________________ 
Composition (% by weight) 
Skin Layers (18% each) 
butene LLDPE 86.4 71.8 
LDPE 9.8 10 
Parapol 1300 4.0 
Eastman E1003 6.9 
Hexene LLDPE-E1003 carrier 11.3 
Trilene CP40-38 
Core Layer (64%) 
hexene LLDPE 96.8 91.8 
Parapol 1300 3.2 
Eastman E1003 3.1 
Hexene LLDPE-E1003 carrier 5.1 
Trilene CP40-38 
Total Tackifier (%) 3.5 4.5 
Test Results 
Noise LEQ (dB) 89 70.1 
Cling @ 200% (grams) 135 150 
______________________________________ 
These tests show the difference in low noise tackifier performance between 
different ethylene-propylene copolymers. The EP copolymers of our 
invention (Trilene CP40-38 and Eastman E1003) provide low unwind noise and 
good cling development in 3-7 days. Other available EP copolymers (Eastman 
E1010 and the Polytech PX-4) also provide low noise, but require 14-28 
days to develop adequate cling. Polybutene tackified films are also 
included for comparison as they are widely used in industry. Polybutene 
tackified films develop high levels of cling rapidly with high unwind 
noise.

EXAMPLE ONE 
In Example One, an EP copolymer, trade name Eastman E1003, with a number 
average molecular weight (M.sub.n) of 2142, a weight average molecular 
weight (M.sub.w) of 11812, a "Z" average molecular weight (M.sub.z) of 
40158, a polydispersity index (Q=M.sub.w /M.sub.n) of 5.51, an ethylene 
content by percentage of 22% and a melt index (MI) of &gt;207 grams/10 min. 
is added to LLDPE stretch film. The Eastman E1003 has been used in the 
prior art as a hot melt additive and not as a film tackifying agent. A 
monolayer film would consist of 4-6% of the Eastman E1003 EP copolymer 
while the remaining 96-94% of the film is comprised of butene comonymer 
LLDPE. These films had no unwind noise and had adequate cling 3 days after 
extrusion. 
A coextruded film consists of two skin layers and one core layer. In a 
coextruded film form each skin layer comprises 18% of the whole film form 
and the core layer comprises 64% of the whole film form. The entire 
coextruded film form is made up of 4.5% of the EP copolymer. The Eastman 
E1003 EP copolymer comprises 6.9% of each skin layer and 3.1% of each core 
layer. The base resin of a butene comonymer LLDPE makes up the remaining 
percentage of the film. 
In the situation where Eastman E1003 comprises 4.5% of the coextruded film 
structure, the properties of Eastman E1003 reduce the noise that the film 
makes upon stretching to 70 dB, or approximately 20 dB lower than 
polybutene tackified films. 
EXAMPLE TWO 
Blends were made of a butene comonymer LLDPE and an EP copolymer 
concentrate, Polytech PX-4. The EP copolymer in PX-4 has a M.sub.n of 
2073, a M.sub.w of 30615, a M.sub.z of 146380, a Q of 9.94, and an 
ethylene content of 28%. PX-4 was added to the butene comonymer LLDPE 
stretch film. The blend consisted of 5.5% by weight of Polytech PX-4 in a 
monolayer stretch film. 
The results of testing done on the Polytech PX-4 and LLDPE blend stretch 
film showed a reduction in noise of the film upon peeling from the roll 
and an increase in cling. Testing of this embodiment also revealed that 
higher loads or concentrations of the Polytech PX-4 were needed to produce 
the same good cling properties as the other embodiments discovered of this 
invention. In order to produce the same good cling as the other 
embodiments of this invention, the percentage by weight of the Polytech 
PX-4 was increased to 10% by weight of the blend. At such an increased 
percentage, the Polytech PX-4 exhibits 100 grams cling at 200% stretch in 
approximately 27 days after the stretch film is blown. The Polytech PX-4 
does not develop adequate cling at this percentage by weight until between 
14 and 28 days after extrusion. 
EXAMPLE THREE 
In Example Three, a blend of a LLDPE and an EP copolymer, tradename of 
Trilene CP40-38, with a M.sub.n of 2471, a M.sub.w of 7289, a M.sub.z of 
4630, a Q of 2.95, and an ethylene content of 26% by weight was added to 
the LLDPE to form a blend. The blends consist of between 4-6% by weight of 
the Trilene CP40-38 in a monolayer of the stretch film formula or 4 to 5% 
of the Trilene CP40-38 in a coextruded film formula. At such percentages 
by weight, the EP copolymer-stretch film blend exhibited a reduction in 
peel-off roll noise compared to polybutene tackified film and an increase 
in cling. 
A coextruded film with 3.5% by weight of the Trilene at 200% percent 
stretch, the noise level of the peel-off was significantly reduced to 
approximately 65-68 dB. At 5% by weight of the Trilene CP40-38, in a 
monolayer film exhibited good cling after one day. The cling at 200% 
remained consistent at approximately 200 grams from approximately 7 days 
after the film was blown. Trilene EP40-38 exhibits excellent noise 
reduction at lower percentages by weight than other embodiments discovered 
of this invention. 
EXAMPLE FOUR 
In Example Four, a blend of LLDPE and an EP copolymer, tradename of Eastman 
E1010, with a M.sub.n of 2912, a M.sub.w of 19955, a M.sub.z of 69055, a Q 
of 6.85, and an ethylene content of 9% by weight was added to the LLDPE 
stretch film to form a blend. The blends consist of between 4-6% by weight 
of the Eastman E1010 in a monolayer of the stretch film formula. At such 
percentage by weight, the EP polymer-stretch film blend exhibited a 
reduction in peel-off roll noise and no increase in cling. 
The Eastman E1010 exhibited the lowest cling of any of the other 
embodiments of the invention disclosed. At 4% and 5% by weight of the 
Eastman E1010, the stretch film had 0 grams at 200% stretch after 28 days. 
Such cling development was significantly lower than any of the other 
embodiments. Due to its and the Polytech PX-4 relatively higher weight 
average molecular weights from the other embodiments, these additives did 
not bleed-out or migrate to the skin layers as quickly as the Trilene 
CP40-38 or the Eastman E1003. 
Tackifying agents which are found to be unacceptable due to either high 
noise or low cling are the Eastman E1010, the Polytech PX-4, and 
polybutene as a tackifying agent.