Molding composition and articles formed thereof

Patent metadata

Field	Value
Publication number	US-11447622-B2
Application number	US-202016947077-A
Country	US
Kind code	B2
Filing date	Jul 17, 2020
Priority date	Jul 19, 2019
Publication date	Sep 20, 2022
Grant date	Sep 20, 2022

Abstract

Articles having improved properties are disclosed. The articles are formed from a composition obtained by dry blending: a) 70-95 wt. % of a polyolefin polymer selected from polypropylene homopolymers, polypropylene copolymers, polypropylene impact copolymers, and mixtures thereof; and b) 5 to 30 wt. % of a free-flowing styrenic block copolymer coated with a functional dusting agent having a maximum particle size of 100 microns. The free-flowing styrenic block copolymer requires less than 400 lbs/ft2 of force to break in a blocking test. The molded article has improved impact strength and haze.

First claim

The invention claimed is:

1. A molding composition comprising:
75 to 95 wt. % of a polyolefin polymer selected from polypropylene homopolymers, polypropylene copolymers, polypropylene impact copolymers, and mixtures thereof; and
5 to 25 wt. % of a styrenic block copolymer coated with a functional dusting agent having a maximum particle size of 100 microns, in an amount of less than 1 wt. % and at least 0.01 wt. %, based on total weight of the styrenic block copolymer,
wherein the functional dusting agent is selected from modified sorbitols, benzoic acid salts, substituted benzoic acid salts, dicarboxylate metal salts, hexahydrophthalic acid metal salts, phenylphosphonic acid salts, phosphate ester salts, glycerolate salts, norbornane carboxylic acid salts, diamides, trisamides and derivatives thereof, tetramides, pine rosin derivatives, acetals and derivatives thereof, di-acetal derivatives, 2,6-naphthalene dicarboxamides, polyvinylcyclohexanes and combinations thereof;

wherein the functional dusting agent is used to coat the styrenic block copolymer forming a coated styrenic block copolymer prior to mixing the coated styrenic block copolymer with the polyolefin polymer to form the molding composition;
wherein the coated styrenic block copolymer is free-flowing, requiring a force of less than 400 lbs/ft 2 to break in a blocking test;
wherein a molded article comprising the molding composition has a notched Izod impact strength of at least 42 J/m, measured at 23° C. in accordance with ASTM D 256, and a haze value, measured according to ASTM D 1003, of 95% or lower.

2. The molding composition of claim 1 , wherein the molded article has a haze value which is at least 2.5% less, compared to a reference molded sample formed from a pre-compounded composition comprising same amounts of the polyolefin, styrenic block copolymer, and functional dusting agent.

3. The molding composition of claim 1 , wherein the molded article comprising the molding composition has a notched Izod impact strength of 50-600 J/m, measured according to ASTM D 1003.

4. The molding composition of claim 1 , further comprising at least one additive selected from antioxidants, fillers, UV stabilizers, slipping agents, flame retarders, blowing agents, and antistatic agents, and wherein the additive is present in an amount of up to 2 wt. %, based on the overall weight of the molding composition.

5. The molding composition of claim 1 , wherein the styrenic block copolymer comprises any of:
a) a tetra-branched block copolymer (IV) having a styrene equivalent peak molecular weight (Mp) of 53,600 to 1,000,000 g/mol, represented by a formula (A-B) 4 X;
b) a tri-branched block copolymer (III) having a Mp of 40,200 to 750,000 g/mol, represented by a formula (A-B) 3 X;
c) a di-branched block copolymer (II) having a Mp of 26,800 to 500,000 g/mol, represented by a formula (A-B) 2 X; and
d) a linear diblock copolymer (I) having a Mp of 13,400 to 250,000 g/mol, represented by a formula A-B;
wherein A represents a polymer block of a mono alkenyl arene; B represents a polymer block of at least one conjugated diene; and X represents residues of a coupling agent.

6. The molding composition of claim 1 , wherein the styrenic block copolymer consists essentially of a diblock copolymer comprising one block of a monovinylaromatic hydrocarbon and one block of a conjugated diene, and has a Mp from 13,400 g/mol to 250,000 g/mol, a vinyl content from 5 to 80 mol % based on the number of repeat monomer units in the conjugated diene block, and a polystyrene content from 20 wt. % to 55 wt. %.

7. The molding composition of claim 1 , wherein the styrenic block copolymer consists essentially of a triblock copolymer comprising at least two blocks of the mono alkenyl arene and at least one block of the conjugated diene;
wherein the triblock copolymer has
a linear block copolymer having a sequential A-B-A structure, or a radial block copolymer having a (A-B) n X structure, where n=2 to 6, A represents a polymer block of a mono alkenyl arene, B represents a polymer block of at least one conjugated diene, and X is residue of a coupling agent;
a Mp of 10.00 g/mol to 500,000 g/mol,
a vinyl content from 5 to 80 mole percent based on the number of repeat monomer units in the conjugated diene block, and
a polystyrene content from 10% to 40%; and

wherein the styrenic block copolymer has a melt index from about <1 g/10 min. to 1,000 g/10 min. as determined by ASTM D-1238, condition G (200° C., 5 kg).

8. The molding composition of claim 7 , wherein the triblock copolymer has a structure (A-B)nX, and wherein the (A-B) 2 molecular weight is 1.5 to 2.5 times peak molecular weight of the (A-B) 1 diblock copolymer.

9. The molding composition of claim 1 , wherein the styrenic block copolymer is a linear hydrogenated block copolymer consisting of a structure A1-B1-A2-B2; wherein each polymer block B1 and B2 comprises polymerized, hydrogenated diene monomer units, and each polymer block A1 and A2 comprises polymerized mono alkenyl arene monomer units; and
wherein the linear hydrogenated block copolymer has a Mp between 6,000 and 8,000 g/mol for the A1 block, between 55,000 and 70,000 g/mol for the B1 block, between 7,500 and 9,000 g/mol for the A2 block and between 5,000 and 12,000 g/mol for the B2 block.

10. The molding composition of claim 1 , wherein the styrenic block copolymer is selectively hydrogenated.

11. A process for forming an article, comprising:
a) providing a polyolefin polymer selected from polypropylene homopolymers, polypropylene copolymers, polypropylene impact copolymers, and mixtures thereof;
b) providing a styrenic block copolymer;
c) providing a functional dusting agent selected from modified sorbitols, benzoic acid salts, substituted benzoic acid salts, dicarboxylate metal salts, hexahydrophthalic acid metal salts, phenylphosphonic acid salts, phosphate ester salts, glycerolate salts, norbornane carboxylic acid salts, diamides, trisamides and derivatives thereof, tetramides, pine rosin derivatives, acetals and derivatives thereof, di-acetal derivatives, 2,6-naphthalene dicarboxamides, polyvinylcyclohexanes and combinations thereof, and wherein the functional dusting agent has a maximum particle size of 100 microns;
d) coating the styrenic block copolymer with the functional dusting agent forming a coated styrenic block copolymer;
e) mixing the coated styrenic block copolymer with the polyolefin polymer forming a molding composition; and
f) forming an article from the molding composition;
wherein the molding composition has 5 to 25 wt. % of the coated styrenic block copolymer and 75 to 95 wt. % of the polyolefin;
wherein the functional dusting agent for coating the stytenic block copolymer is present in an amount of less than 1 wt. % and at least 0.01 wt. %, based on the weight of the styrenic block copolymer;
wherein the coated styrenic block copolymer requires force of less than 400 lbs/ft 2 to break in a blocking test,
wherein the article has a notched Izod impact strength of 42 J/m or higher, measured at 23° C. in accordance with ASTM D256, and a haze value of 95% or lower.

12. The process of claim 11 , wherein the article is formed by molding, and wherein forming the article comprises:
melt-blending the molding composition;
injecting the molding composition into a mold forming a molded article.

13. The process of claim 11 , wherein the article has a haze value that is at least 2.5% less, compared to a reference article formed by molding a pre-compounded composition comprising same amounts of polyolefin, styrenic block copolymer, and functional dusting agent.

14

Assignees

• Kraton Polymers Llc

Inventors

• Raghavendran Venkat
• Wright Kathryn
• Brothers Aaron

Classifications

• C08J2323/12

  Polypropene · CPC title

• B29C45/0001

  characterised by the choice of material · CPC title

• C08K5/005

  Stabilisers against oxidation, heat, light, ozone · CPC title

• C08L23/14 Primary

  Copolymers of propene (C08L23/16 takes precedence) · CPC title

• C08J3/005 Primary

  Processes for mixing polymers · CPC title