Processing additives and uses of same in rotational molding

Patent metadata

Field	Value
Publication number	US-11312043-B2
Application number	US-201113323173-A
Country	US
Kind code	B2
Filing date	Dec 12, 2011
Priority date	Dec 13, 2010
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

The cycle time of polymer compositions subjected to a rotomolding process is improved (i.e., reduced), while the processing window is simultaneously enlarged through the use of a polymer-stabilizing amount of a processing stabilizer system having at least one chroman-based compound according to Formula V:

First claim

We claim:

1. A process for producing a stabilized polymeric hollow article in a rotational molding operation, the process comprising:
a) filling a mold with a polyolefin and 0.01 to 10% by weight of the total weight of the polyolefin of a stabilizer composition, wherein said stabilizer composition comprises:
i) vitamin E acetate;
ii) a phosphite or phosphonite compound; and
iii) at least one basic co-additive selected from calcium stearate, zinc stearate, magnesium behenate, magnesium stearate, sodium ricinoleate, or potassium palmitate;
b) rotating the mold around at least one axis while heating the mold in an oven for a time interval sufficient to achieve sintering and laydown of the polyolefin, thereby spreading the polyolefin to the walls of the mold;
c) cooling the heated mold; and
d) opening the mold to remove a resulting product in the form of a stabilized polymeric hollow article;
wherein the polyolefin comprises linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), or polypropylene; and
wherein the polyolefin, phosphite or phosphonite compound, and at least one basic co-additive, and amounts of the vitamin E acetate, phosphite or phosphonite compound, and at least one basic co-additive are selected to reach maximum mean failure energy (MFE) of the article at a shorter time interval of the rotational molding operation, to retain a higher MFE of the article over a longer heating time of the rotational molding operation, and to enlarge a processing window of the rotational molding operation to a peak internal air temperature (PIAT) of up to 452° F. with yellowness index of the article remaining substantially unchanged up to a PIAT of 452° F., even in the absence of a sterically hindered amine light stabilizer (HALS).

2. The process of claim 1 , wherein the polyolefin is linear low density polyethylene (LLDPE).

3. The process of claim 1 , wherein the phosphite or phosphonite compound is a phosphite compound.

4. The process of claim 3 , wherein the phosphite compound is selected from tris(2,4-di-tert-butylphenyl)phosphite and bis(2,4-dicumylphenyl)pentaerythritol diphosphate.

5. The process of claim 1 , wherein the at least one basic co-additive is zinc stearate.

6. The process of claim 1 , wherein 0.05% by weight of the vitamin E acetate, 0.06% by weight of the phosphite, and either 0.035% or 0.05% by weight of the zinc stearate are present based on the total weight of the polyolefin.

7. The process of claim 1 , wherein the article has a ⅛″ to ¼″ thickness.

8. The process of claim 1 , wherein the polyolefin and amounts of the vitamin E acetate, the phosphite or phosphonite compound, and the basic co-additive in the stabilizer composition are further selected to reduce a heating time of the rotational molding operation for achieving optimal cure without compromising physical and/or mechanical properties of the article.

Assignees

• Gupta Ram
• Samuels Sari Beth
• Steele Thomas
• Eng J Mon Hei
• Cytec Tech Corp

Inventors

• Gupta Ram
• Samuels Sari-Beth
• Steele Thomas
• Eng J Mon Hei

Classifications

• C08K5/3492

  Triazines · CPC title

• C08K5/13

  Phenols; Phenolates · CPC title

• C08K5/098

  Metal salts of carboxylic acids · CPC title

• B29K2023/0625

  LLDPE, i.e. linear low density polyethylene · CPC title

• Y02P20/10

  Process efficiency · CPC title