Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-15
2003-02-04
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S352000, C428S035100, C428S036800
Reexamination Certificate
active
06515076
ABSTRACT:
TECHNICAL FIELD
The present invention relates to polyethylene resin and its compounds for container uses, and containers. More specifically, the present invention relates to polyethylene resin or its compounds which realize molding of thin-walled articles and high-speed molding, achieves/achieve excellent printability and stress cracking resistance and are suitable for container uses involving tubes, bottles, etc. and containers.
BACKGROUND ART
Containers such as tubes for cosmetics, shampoo and detergent, food packaging tubes for mayonnaise, etc., and food packaging bottles for soy sauce, etc. usually have small wall thickness and are manufactured in the blow molding method. These containers are constructed of, for example, either a single layer of high-pressure low-density polyethylene, or two layers consisting of a high-pressure low-density polyethylene layer and a high-density polyethylene layer. The aforesaid container is required to have excellent properties such as environmental stress cracking resistance (ESCR), printability, etc.
The recent trend has been such that improvement in the productivity of these tubes was strongly desired. In order to achieve the improvement in the productivity, studies have been made on approaches to high-speed tube forming processes using linear low-density polyethylene (L-LDPE). Although use of the linear low-density polyethylene of the conventional type certainly facilitates tube forming at high speed, this approach is accompanied by such problem that printing is totally hampered due to the bleeding phenomenon caused by the solvent used in printing ink during the process of printing executed on the surface of the tube.
Such being the case, circles interested have been looking forward to an introduction of such polyethylene resin or its compounds that realizes/realize molding of thin-walled articles and high speed molding, achieves/achieve excellent printability and stress cracking resistance and is/are suitable for container uses involving tubes, bottles, etc.
The present invention is intended to resolve the aforesaid problems associated with the conventional technology, and it does provide such polyethylene resin and its compounds that realize molding of thin-walled articles and high speed molding, achieve excellent printability and stress cracking resistance, and are suitable for container uses involving tubes, bottles, etc., and containers.
DISCLOSURE OF THE INVENTION
Polyethylene resin and its compounds of the present invention comprise a polyethylene resin and resin compounds for container uses, that achieve a 50% cracking appearance time (F
50
) (the elapsed time when 50% of specimens fail), which is an index of stress cracking resistance, of 100 or more hrs. and demonstrate the characteristic of being substantially free of any peel area (the area of defect loss part) on the printed surface in a squared cut test performed on film produced therefrom.
The polyethylene resin for container uses of the present invention represents a polyethylene resin and resin compounds comprising linear polyethylene (A) satisfying the following requirements,
(i) Molecular weight distribution (Mw/Mn) as determined by GPC is 2-3.5,
(ii) Density is 0.890-0.975 g/cm
3
, and
(iii) Content of component soluble in n-decane at room temperature is 2% by weight or less;
which achieves a 50% cracking appearance time (F
50
) of 100 or more hrs. and demonstrates the characteristics of being substantially free of any peel area on the printed surface in a squared cut test performed on film produced therefrom.
The polyethylene resin and its compounds for container uses, respectively, of the present invention achieves/achieve a 50% cracking appearance time (F
50
), which is an index of stress cracking resistance, of 100 or mores hrs.
The polyethylene resin and its compounds for container uses, of the present invention are required to have such excellent stress cracking resistance as described above and, at the same time, achieve such excellent printability that the printed surface does not substantially get peeled off in a squared cut test performed on film produced from said polyethylene resin and its compounds.
While a detailed explanation is furnished afterwards about the squared cut test, the phrase “does not substantially get peeled off” means that 90% or more, or preferably 95% or more, of coated sections on a specimen film tested in the squared cut test does not get peeled off.
So long as all of the aforesaid requirements are satisfied, the polyethylene resin and its compounds of the present invention can be suitably utilized as resins for container uses.
The linear polyethylene (A) of the present invention comprises a linear polyethylene which satisfies the following requirements.
(i) Molecular weight distribution (Mw/Mn) as determined by GPC is 2-3.5,
(ii) Density is 0.890-0.975 g/cm
3
, and
(iii) Content of component soluble in n-decane at room temperature is 2% by weight or less.
The molecular weight distribution is within the range of 2-3.5, or preferably 2-3. When linear polyethylene (A) whose molecular weight distribution is in the aforesaid range is used, there can be provided containers having excellent environmental stress cracking resistance (ESCR) and printability. The molecular weight distribution as referred to in the present invention means molecular weight distribution (Mw/Mn) wherein “Mw” is weight average molecular weight and “Mn” is number average molecular weight as determined by GPC in accordance with a testing procedure described hereinafter.
The linear polyethylene (A) of the present invention comprises ethylene-&agr;-olefin copolymer obtained by copolymerizing ethylene with &agr;-olefin having 3-20 carbon atoms.
As specific examples of said &agr;-olefin, there can be cited &agr;-olefins having 3-20 carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Preferred ones among the aforesaid &agr;-olefins are &agr;-olefins having 3-8 carbon atoms such as 1-hexene, 4-methyle-1-pentene, and 1-octene.
The linear polyethylene (A) as used in the present invention contains the structural unit derived from ethylene of usually 95-99 mol. %, preferably 96-98 mol. %, and the structural unit derived from &agr;-olefin having 3-20 carbon atoms at a mol. ratio of usually 1-5 mol. %, preferably 2-4 mol. %.
This linear polyethylene (A) has a density of 0.890-0.975 g/cm
3
, preferably 0.900-0.960 g/cm
3
, more preferably 0.900-0.950 g/cm
3
, furthermore preferably 0.910-0.930 g/cm
3
. When linear polyethylene (A) of a density falling in said ranges is used, there can be provided containers having excellent environmental stress cracking resistance (ESCR) and printability.
The liner polyethylene (A) as used in the present invention contains 2% by weight or less of component soluble in n-decane at room temperature, or preferably 1% by weight or less. When linear polyethylene (A) containing 2% by weight or less of solubles in n-decane at room temperature is used, there can be provided containers having excellent printability. The less component soluble in n-decane at room temperature are, the narrower becomes the composition distribution.
It is preferable that the linear polyethylene (A) of the present invention satisfies the following relationship between the melt tension (MT) (g) at a temperature of 190° C. and the melt flow rate (MFR)(g/10 min.).
MT>2.2×MFR
−0.84
(i)
It is preferable that the linear polyethylene (A) of the present invention satisfies the following relationship between the quantity of component soluble in decane at room temperature (W)(% by weight) and the density (d)(g/cm
3
).
When MFR≦10 g/10 min.,
W
<80×exp(−100(d−0.88))+0.1 (ii-a)
When MFR>10 g/10 min.,
W
<80×(MFR−9)
0.26
×exp(−100(d−0.88))+0.1 (ii-b)
It is preferable that the linear polyethylene (A) of the present invention satisfies the following relationship between the highest peak (Tm)(° C.) in the endothermic curve as
Kageyama Fumio
Kimura Tomohiko
Birch & Stewart Kolasch & Birch, LLP
Harlan R.
Mitsui Chemicals Inc.
Wu David W.
LandOfFree
Polyethylene resins and its compounds for container uses and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyethylene resins and its compounds for container uses and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyethylene resins and its compounds for container uses and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3154885