HK1077318A - Ionomer/high density polyethylene blends with improved impact resistance - Google Patents

Description

Ionomer/high density polyethylene blends with improved impact resistance

Technical Field

The present invention relates to maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blends having improved impact resistance. More particularly, but not by way of limitation, the present invention relates to the incorporation of maleic anhydride modified ethylene polymers (such as maleic anhydride grafted high density polyethylene, MAN-g-HDPE; maleic anhydride grafted very low density polyethylene, MAN-g-VLDPE; maleic anhydride grafted ethylene propylene rubber, MAN-g-EPR; or maleic anhydride grafted ethylene propylene diene monomer rubber, MAN-g-EPDM) into ionomer/high density polyethylene blends to improve low temperature izod impact properties.

Background

Thermoplastic alloys based on blends of ionomers and high density polyethylene or polyamide for injection molding exterior automotive color molded instrument panels, bumpers are generally known in the artLever covers, sideforms and other decorative trim. These types of polymer blends are disclosed, for example, in U.S. Pat. nos. 4,387,188 and 5,866,658, respectively. Each of these references relates to copolymers of an alpha-olefin, typically ethylene, copolymerized with an alpha, beta-ethylenically unsaturated carboxylic acid, typically acrylic acid, methacrylic acid or mixtures thereof, wherein the acid copolymer preferably contains from 5 to 80% of acid groups neutralized with a metal ion such as zinc, sodium, or the like. Such ionomers are available under the trade name Surlyn^*From e.i. dupont de Nemours and Company. In the' 188 patent, a partially neutralized acid copolymer is blended with a linear polymer of an alpha-olefin and glass fibers to produce a molding resin. In the' 658 patent, a highly neutralized acid copolymer is blended with one or more polyamides that constitute the continuous or co-continuous phase of the resulting blend. One difficulty with such blends is achieving and maintaining low temperature impact resistance, particularly in the absence of reinforcing fibers.

Summary of The Invention

In view of the above, it has now been discovered that the addition or incorporation of a maleic anhydride modified ethylene-derived polymer (e.g., maleic anhydride grafted high density polyethylene, MAN-g-HDPE; maleic anhydride grafted very low density polyethylene, MAN-g-VLDPE; maleic anhydride grafted ethylene propylene rubber, MAN-g-EPR; or maleic anhydride grafted ethylene propylene diene monomer rubber, MAN-g-EPDM) into an ionomer/high density polyethylene blend improves low temperature izod impact. More specifically, the low temperature Izod impact performance of non-fiber reinforced blends of ionomer/HDPE is essentially doubled by the addition of MAN-g-HDPE.

The present invention therefore provides a maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend having improved impact resistance comprising from 1 to 20 parts by weight of an ethylene polymer modified with from 0.2 to 5.0 wt% maleic anhydride per hundred parts by weight of the ionomer/high density polyethylene blend. Preferably, the ethylene polymer modified with maleic anhydride is selected from the group consisting of maleic anhydride grafted high density polyethylene (MAN-g-HDPE), maleic anhydride grafted very low density polyethylene (MAN-g-VLDPE), maleic anhydride grafted ethylene propylene rubber (MAN-g-EPR), maleic anhydride grafted ethylene propylene diene monomer rubber (MAN-g-EPDM), and mixtures thereof.

The present invention further provides a method of improving the impact resistance of an ionomer/high density polyethylene blend comprising the steps of:

(i) adding 1 to 20 parts by weight of a maleic anhydride modified ethylene polymer per hundred parts by weight of the cumulative amount of ionomer and high density polyethylene; and

(ii) the maleic anhydride modified ethylene polymer, ionomer, and high density polyethylene are mixed at high temperature and high shear rate.

Most preferably, the polyethylene modified with maleic anhydride is maleic anhydride grafted high density polyethylene (MAN-g-HDPE).

Modes for carrying out the invention

The present invention relates to the addition of maleic anhydride modified ethylene polymers to ionomer/high density polyethylene blends to maintain or improve the impact resistance of the resulting blend. For the purposes of describing the present invention, unless otherwise specified, the term "copolymer" means a polymer derived from the polymerization of two or more different monomers that are the reactants of choice during polymerization. The term copolymer itself is intended to include both: "terpolymers" and polymers produced from more than three comonomers also include "dipolymers". While micro-analysis may reveal dispersed, continuous, and/or discontinuous phase states, the term "blend" is intended to mean a polymer combination, mixture, and/or plurality of polymers, with or without additives, that act together or result in a thermoplastic matrix or polymer alloy. Likewise, the phrase "consisting of …" means that the listed components are required, while minor amounts of other components may be present to the extent that they do not detract from the operability of the invention. Rather, the term "comprising" is intended to acknowledge that significant amounts of other components may be present, provided that some of the benefits and/or advantages of the present invention (e.g., improved or maintained impact properties, etc.) are still achieved.

The ionomer/high density polyethylene blends used according to the present invention broadly include any such thermoplastic alloy based on combining or mixing: neutralized or partially neutralized ethylene/α, β -unsaturated carboxylic acid copolymers (referred to herein as acid copolymers) are combined with thermoplastic linear polyethylenes. Such blends can and typically are reinforced with various fibers. These types of polymer blends with reinforcing fibers are disclosed, for example, in U.S. Pat. No. 4,387,188. As taught in this reference, the acid copolymer content of the blend is typically 38 to 90 weight percent of the blend; however, it is now contemplated that 20-80 wt% acid copolymer is a more preferred range. Such acid copolymers that produce ionomers are also described in U.S. patents 3,520,861, 4,026,967, 4,252,924, and 4,248,990. Neutralized and partially neutralized ionic copolymers (ionomers) are described in U.S. Pat. No. 3,264,272.

The high density polyethylene of the ionomer/HDPE blend according to the present invention can be any such thermoplastic linear polyolefin generally known in the art. The polyethylene has a density of from about 0.91 to 0.97, preferably from 0.935 to about 0.970, and most preferably from 0.95 to about 0.97. HDPE is typically characterized by a melt index as follows: generally in the broad range of 0.1 to 100, but preferably from about 0.3 to about 10, most preferably from about 2 to about 6 for injection molded grades and less than 2 for film and blow molded grades. HDPE itself is a higher molecular weight polymer based on ethylene, with no or small amounts of other copolymerized alpha-olefins, resulting in a linearity typically characterized as about 8 or less branch points per thousand carbon atoms, as is generally known in the art. The HDPE content of the blend is typically 20 to 80 wt%, preferably 50 to 75% and most preferably 60 to 70 wt% of the blend.

The maleic anhydride modified ethylene polymer impact additive preferably contains 0.2 to 5.0 weight percent maleic anhydride comonomer or equivalent acid content incorporated into the ethylene polymer. For the purposes of the present invention, it is contemplated that other unsaturated dicarboxylic acids such as fumaric, itaconic and mesaconic acids, which are structurally closely related to and potentially precursors to similar anhydrides after the grafting reaction, should be considered equivalent to MAN in the MAN-modifying additive. The actual grafting reaction for introducing maleic anhydride onto the ethylene polymer can be carried out by essentially any method generally known in the art. The impact modified blends of the present invention may contain up to about 20 weight percent of a Maleic Anhydride (MAN) modified ethylene polymer incorporated into the ionomer/high density polyethylene blend as an impact additive. However, for the purposes of this invention, it is to be understood that the benefits of this invention can be partially realized at maleic anhydride modified polymer loading levels of greater than 20 wt% and in such cases should be considered equivalent to the purposes of this invention.

For the purposes of the present invention, the ethylene polymer modified by reaction with maleic anhydride or an equivalent dicarboxylic acid may generally be any thermoplastic or elastomeric polymer composition derived from polymerizing predominantly ethylene monomers. This material itself includes essentially any polyethylene polymer or polyethylene copolymer generally known in the art. Preferably, the ethylene polymer comprises High Density Polyethylene (HDPE), Very Low Density Polyethylene (VLDPE), Ethylene Propylene Rubber (EPR) including ethylene propylene diene rubber (EPDM), and the like. As shown in the accompanying examples, the addition of about 10 wt% maleic anhydride modified HDPE significantly affected the low temperature Izod impact properties.

Indeed, the impact modified blends of the present invention advantageously contain minor amounts, typically up to several percent, of other additives such as pigments, colorants, carbon black, ultraviolet light stabilizers, antioxidants, processing aids, glass fibers, inorganic fillers, anti-slip agents, plasticizers, nucleating agents, and the like. Various such additives and their respective uses are well known in the art and are used commercially in association with ionomer/HDPE blend applications. Typical preferred combinations are specified in the examples.

The preparation of the blends according to the invention can be carried out using standard mixing practices, as is generally known in the art. Preferably a commercial mixer such as a Banbury or commercial thermoplastic extruder, especially a twin screw extruder or the like is used to achieve thorough mixing of the components and to obtain uniform dispersion of the components. Or the final dispersion may be achieved in the final injection molding or extrusion of the article manufactured starting from the individual components, intermediates, component precursors, or some combination of these. The blending may also be carried out in stages, depending on the choice and availability of the initial components. The commercially available ionomer/HDPE blend itself can be directly coextruded with the maleic anhydride modified ethylene polymer impact additive. Or the ionomer, HDPE, and maleic anhydride modified ethylene polymer can be co-extruded simultaneously to obtain the desired blend. It is further contemplated that the degree of neutralization of the ionomer can be purposefully enhanced by the addition of metal hydroxides, metal oxides, and the like during the blending step. It is further contemplated that HDPE and maleic anhydride modified ethylene polymer may be employed along with an unsaturated carboxylic acid (E/AA or E/MAA) copolymer precursor to the ionomer during coextrusion along with a neutralized metal component, thereby producing the ionomer in situ during blending.

The following examples are presented to more fully demonstrate and further illustrate various aspects and features of the present invention. The illustrations themselves are intended to further illustrate the differences and advantages of the present invention, but are not intended to be unduly limiting. In the following examples, all blends were extrusion compounded on a ZSK-30 co-rotating twin screw extruder, typically using the following temperature profiles, unless otherwise noted:

feeding: cold

Region 1: 150 ℃ C

Region 2: 225 deg.C

Region 3: 225 deg.C

Region 4: 225 deg.C

Die (single bar, 1/4 inch diameter): 230 deg.C

Screw speed: 200rpm

Output rate: 15-20lb/hr

Melting temperature: typically 245 ℃ and 260 DEG C

Test bars (5 inches x 1/2 inches x 1/8 inches), test pieces (3 inches x 5 inches x 1/8 inches) and trays (3 inches x 1/8 inches) for physical testing were molded using a single screw injection molding machine, typically using the following temperature profiles and conditions:

rear part: 220 deg.C

Center: 225 deg.C

Front part: 230 deg.C

A nozzle: 230 deg.C

A mould: 25 deg.C

The pressure head speed: fast-acting toy

Screw speed: 60rpm

Injection time: 35 seconds

Retention time: 25 seconds

Back pressure: 50psig

Various test conditions for measuring physical properties were used. Melt Index (MI) was measured according to ASTM D1238 condition E at 190 ℃ and 2, 160 gram load. Tensile properties were measured according to ASTM D1708 using a (1.vz inch x 5/8 inch x 1/8 inch) bar die cut from a test strip (3 inch x 5 inch x 1/8 inch). Measurements were made on an Instron with a crosshead speed of 2 inches/minute. Flexural modulus was measured according to ASTM D790 using a 2 inch span on a (5 inch by 1/2 inch by 1/8 inch) test bar. Notched Izod impact performance was measured according to ASTM D256 using a (2.vz inches x 1/2 inches x 1/8 inches) bar with a 0.1 inch notch machined to the side of the bar. The bars were obtained from a single 5 inch x 1/2 inch x 1/8 inch molded bar, which was then cut in half (i.e., one near the die entrance and the other at the distal end). Dynatup instrumental impact measurements were performed in a vertical mode on 3 inch x 1/8 inch disks at a Tup size of 1/2 inches and a drop speed of 5mph (i.e., 10 inch drop height under 98.2 pound load) in accordance with ASTM D3763.

The starting raw materials, their characterization and respective commercial sources are summarized below:

alathon * 7030-HDPE, MI 2.8(Spec range 2.4-3.2) (LyondellPetrochemical Co.).

Chimassorb * 944 FD-hindered amine light stabilizer (Ciba-Geigy Corp.).

Flexomer DFDB 9042-ethylene/butene VLDPE, -15% butene, density-0.900, MI-5 (Union Carbide Corp.).

Flexomer DFDU 1085-ethylene/butene VLDPE, > 15% butene, density 0.884-0.900, MI 3-4(Union Carbide Corp.).

Fusabond * E MB-100D-MAN-modified Sclair 2907 HDPE; about 1% MAN, MI ═ 2 (modified polymer, DuPont of Canada).

Fusabond * N MN-493D-MAN modified Engage8180 VLDPE, 0.5% MAN, MI 1.3.

Fusabond * N MF-520D; MAN modified Nordel * IP3745P, MAN-g-ethylene/propylene/hexadiene terpolymer (DuPont). About 0.5% MAN, MI 1.3

Irganox * 1010 ═ tetrakis (methylene (3, 5-di-tert-butyl-4-hydroxycinnamate) (Ciba-Geigy Corp.).

Irganox * B215 ═ 1: 2/Irganox * 1010/Irgafos 168 blends. Irgafos 168 ═ tris (2, 4-di-tert-butylphenyl) phosphate (Ciba-Geigy Corp.).

Norde1 * 2722 ═ narrow molecular weight distribution elastomer, 72/21/7: ethylene/propylene/hexadiene terpolymer (DuPont).

Surlyn * 9520-90/10: an E/MAA copolymer, 68-71% neutralized with zinc, base resin MI 33; ionomer MI 1.1.

Tinuvin * 770 DF ═ UV stabilizers (Ciba-Geigy Corp.).

Example 1

A series of blends of seven different high density polyethylenes and ionomers were prepared and tested as described above by conventional methods. Six trials involved Maleic Anhydride (MAN) modified high density polyethylene (Sclair 2907 HDPE) available from DuPont of Canada under the trade designation Fusabond * E MB-100D (MAN-g-HDPE;. about.1% MAN, MI ═ 2). Details of the compositions and resulting data are given in table 1. As shown in the table, the addition of Fusabond * E MB-100D, a maleic anhydride-modified polyethylene, increased the low temperature notched Izod impact performance by at least two times without a decrease in flexural modulus.

TABLE 1

Test of	1	2	3	4	5	6	7
								ALATHON*7030	60.05％	50.05％	47.55％	47.55％	47.55％	45.05％	45.05％
SURLYN*9520	36.30％	36.30％	33.80％	33.80％	33.80％	31.80％	31.80％
								IRGANOX*1010	0.15％	0.15％	0.15％	0.15％	0.15％	0.15％	0.15％
NORDEL*2722	-	-	5.0％	-	-	-	-
								Flexomer DFDB9042	-	-	-	5.0％	-	10.0％	-
Flexomer DFDU1085	-	-	-	-	5.0％	-	10.0％
								ZnO(CS8749-5)	3.50％	3.50％	3.50％	3.50％	3.50％	3.50％	3.50％
Fusabond*EMB-100D	-	10.0％	10.0％	10.0％	10.0％	10.0％	10.0％
Flexural modulus (psi)	115,300	119,300	106,400	105,600	106,500	101,600	102,100
								Tensile at yield (psi)	3,250	3,270	3,030	3,110	3,120	2,930	3,030
Elongation at yield (%)	12％	12％	13％	12％	12％	13％	12％
								Maximum elongation (psi)	3,250	3,700	3,400	3,410	3,610	3,150	3,250
Maximum tensile elongation (%)	12％	350％	360％	380％	370％	370％	390％
								Breaking tension (psi)	3,200	3,700	3,390	3,410	3,590	3,140	3,430
Break-offElongation at Break (psi)	200％	360％	360％	380％	370％	380％	400％
								Notched Izod impact at-30 ℃
Die inlet end	9.51	20.2	21.7	20.3	21.5	18.2	21.4
								Distal end	10.11	21.4	27.4	26.6	22.6	22.1	22.3
Dynatup instrument impact at-30 ℃
								Punching machineImpact energy (ft-pound)		80.9	81.7	81.4	80.7	80.8	80.7
Total energy (ft-pound)		27.0	24.9	27.9	26.2	26.7	28.6
Melt tension (cN)	13.6	14.1	12.3	9.0	9.4	9.8	10.7

Example 2

In a manner similar to example 1, a series of seven additional high density polyethylene and ionomer blends were prepared and tested. Run 1 was essentially a repeat of run 2 of example 1, using 10 wt% maleic anhydride modified high density polyethylene (Fusabond * EMB-100D; MAN-g-HDPE,. about.1% MAN, MI ═ 2) as the impact additive. The other six runs involved the use of maleic anhydride modified very low density polyethylene (Fusabond * N MN-493D; MAN-g-VLDPE,. about.0.5% MAN, MI ═ 1.3) and maleic anhydride modified ethylene propylene hexadiene terpolymer (Fusabond * NMF-520D; MAN-g-EPDM,. about.0.65% MAN, MI ═ 0.6). Details of the compositions and resulting data are given in table 2. As shown in this table, the addition of maleic anhydride modified VLDPE and EPDM showed impact improvement relative to the control (test 1 of example 1), but not as significant as the improvement obtained with the MAN-g-HDPE additive.

TABLE 2

Test of	1	2	3	4	5	6	7
								ALATHON*7030	50.05％	52.90％	52.90％	50.05％	50.05％	50.14％	50.05％
SURLYN*9520	36.30％	38.45％	38.45％	36.30％	36.30％	36.21％	36.30％
								IRGANOX*1010	0.15％	0.15％	0.15％	0.15％	0.15％	0.15％	0.15％
ZnO(CS8749-5)	3.50％	3.50％	3.50％	3.50％	3.50％	3.50％	3.50％
								FUSABOND E MB-100D	10.00％	5.00％	-	10.00％	10.00％	-	-
FUSABOND N MN-493D	-	-	5.00％	-	-	10.00％	-
								FUSABOND N MF-520D	-	-	-	-	-	-	10.00％
Tensile properties at room temperature
								Tensile at yield (psi)	3,390	3,030	2,740	3,050	3,270	2,410	2,660
Elongation at yield (%)	12％	12％	14％	12％	11％	15％	15％
								Maximum elongation (psi)	3,730	3,710	3,450	3,780	3,880	3,420	3,430
Maximum tensile elongation (%)	360％	330％	290％	360％	350％	300％	300％
								Breaking tension (psi)	3,730	3,710	3,450	3,780	3,790	3,410	3,430
Elongation at break (psi)	370％	330％	290％	370％	350％	297％	300％
								Flexural modulus (psi)	115,300	106,600	83,700	107,900	114,300	70,600	78,800
Notched Izod impact at-30 ℃
								Die inlet end	26.3	18.0	16.6	18.5	18.46	16.6	16.37
Distal end	20.6	23.6	22.7	23.8	23.65	20.0	19.75
								Dynatup instrument impact at-30 ℃
Impact energy (ft-pound)	81.0	77.3	77.2	77.1	78.5	77.6	78.4
								Total energy (ft-pound)	27.2	25.3	25.5	26.7	27.4	26.6	26.8

Industrial applicability

In view of the above, the addition or incorporation of a maleic anhydride modified ethylene-derived polymer (such as maleic anhydride grafted high density polyethylene, MAN-g-HDPE; maleic anhydride grafted very low density polyethylene, MAN-g-VLDPE; maleic anhydride grafted ethylene propylene rubber, MAN-g-EPR; or maleic anhydride grafted ethylene propylene diene monomer rubber, MAN-g-EPDM) to an ionomer/high density polyethylene blend improves low temperature Izod impact properties. The blends exhibiting improved impact properties according to the present invention are particularly useful in the manufacture of automotive parts, instrument panels and the like having a "class a" surface.

Claims (10)

1. A maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend having improved impact resistance comprising, for each hundred parts by weight of ionomer/high density polyethylene blend, 1 to 20 parts by weight of an ethylene polymer modified with 0.2 to 5.0 wt% maleic anhydride.

2. A maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend of claim 1 wherein said ethylene polymer modified with maleic anhydride is selected from the group consisting of maleic anhydride grafted high density polyethylene (MAN-g-HDPE), maleic anhydride grafted very low density polyethylene (MAN-g-VLDPE), maleic anhydride grafted ethylene propylene rubber (MAN-g-EPR), maleic anhydride grafted ethylene propylene diene monomer rubber (MAN-g-EPDM), and mixtures thereof.

3. A maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend of claim 1 wherein said ethylene polymer modified with maleic anhydride is a maleic anhydride grafted high density polyethylene (MAN-g-HDPE).

4. A maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend of claim 1 wherein said ethylene polymer modified with maleic anhydride is a maleic anhydride grafted very low density polyethylene (MAN-g-VLDPE).

5. A maleic anhydride modified ethylene polymer/ionomer/high density polyethylene blend of claim 1 wherein said ethylene polymer modified with maleic anhydride is a maleic anhydride grafted ethylene propylene diene monomer rubber (MAN-g-EPDM).

6. A method of improving the impact resistance of an ionomer/high density polyethylene blend comprising the steps of:

(i) adding 1 to 20 parts by weight of a maleic anhydride modified ethylene polymer per hundred parts by weight of the cumulative amount of ionomer and high density polyethylene; and

(ii) the maleic anhydride modified ethylene polymer, ionomer, and high density polyethylene are mixed at high temperature and high shear rate.

7. The process of claim 6 wherein said ethylene polymer modified with maleic anhydride is selected from the group consisting of maleic anhydride grafted high density polyethylene (MAN-g-HDPE), maleic anhydride grafted very low density polyethylene (MAN-g-VLDPE), maleic anhydride grafted ethylene propylene rubber (MAN-g-EPR), maleic anhydride grafted ethylene propylene diene monomer rubber (MAN-g-EPDM), and mixtures thereof.

8. The process of claim 6 wherein said ethylene polymer modified with maleic anhydride is maleic anhydride grafted high density polyethylene (MAN-g-HDPE).

9. The process of claim 6 wherein said ethylene polymer modified with maleic anhydride is maleic anhydride grafted very low density polyethylene (MAN-g-VLDPE).

10. The process of claim 6 wherein said ethylene polymer modified with maleic anhydride is maleic anhydride grafted ethylene propylene diene monomer rubber (MAN-g-EPDM).