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Polyester blends containing a metal oxide desiccant

Abstrict

Blends of a polyester with a desiccant and a poly(mono-1-olefin); optionally with an oil.

Claims

I claim:

1. A composition consisting essentially of about 50 to 90 weight percent of at least one polyalkylene terephthalate polyester resin, about 3 to 20 weight percent of at least one desiccant, and about 3 to 20 weight percent of at least one normally solid poly(1-alkene); and optionally further about 0.5 to 5 weight percent of a light mineral oil;

wherein said desiccant is at least one of the group consisting of calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide.

2. The composition according to claim 1 including said light mineral oil.

3. The composition of claim 2 employing about 80 to 90 weight percent said polyalkylene terephthalate polyester resin, about 5 to 10 weight percent said desiccant, and about 5 to 10 weight percent said poly(1-alkene); and where present about 1 to 2 weight percent said light mineral oil.

4. The composition of claim 1 wherein said desiccant is a calcium oxide.

5. The composition of claim 1 wherein said polyalkylene terephthalate polyester resin is a polyethylene terephthalate, said desiccant is a calcium oxide, and said poly(1-alkene) is a polyethylene.

6. The composition of claim 5 wherein said polyethylene terephthalate is a PET bottle regrind.

7. The composition of claim 1 consisting of said polyalkylene terephthalate polyester resin, said desiccant, and said poly(1-alkene).

8. A polyester blend composition consisting essentially of effective proportions of:

about 50 to 90 weight percent of a polyalkylene terephthalate polyester resin,

about 3 to 20 weight percent of a desiccant,

about 3 to 20 weight percent of a normally solid poly(1-alkene), and

about 0.5 to 5 weight percent a light mineral oil;

wherein said desiccant is selected from at least one of the group consisting of calcium oxide, magnesium oxide, strontium oxide, barium oxide, and aluminum oxide.

9. The composition according to claim 8 wherein said polyalkylene terephthalate polyester resin is a polyethylene terephthalate.

10. The composition of claim 8 wherein said desiccant is a calcium oxide, and said poly(1-alkene) is a polyethylene.

11. The composition of claim 9 employing about 80 to 90 weight percent said polyethylene terephthalate, about 5 to 10 weight percent said desiccant, and about 5 to 10 weight percent said poly(1-alkene), and about 1 to 2 weight percent said light mineral oil.

12. The composition of claim 11 wherein said desiccant is a calcium oxide, and said poly(1-alkene) is polyethylene.

13. A polyester blend composition consisting of:

about 50 to 90 weight percent polyalkylene terephthalate resin,

about 3 to 20 weight percent of at least one desiccant selected from the group consisting of calcium oxide, magnesium oxide, strontium oxide, barium oxide, and aluminum oxide, and

about 3 to 25 weight percent of a poly(.alpha.-olefin);

and optionally about 0.5 to 5 weight percent of light mineral oil.

14. A polyester blend composition consisting of:

about 50 to 90 weight percent polyethylene terephthalate resin,

about 3 to 20 weight percent of at least one desiccant selected from the group consisting of calcium oxide, magnesium oxide, strontium oxide, barium oxide, and aluminum oxide,

about 3 to 20 weight percent poly(.alpha.-olefin);

and about 0.5 to 5 weight percent of light mineral oil.

Description

FIELD OF THE INVENTION

The invention pertains to improved polyester blends. In another aspect, the invention pertains to blends of a polyester with a desiccant and one or more of a poly(mono-1-olefin), a block copolymer of diene/monovinylarene, and a poly(monovinylarene). In another aspect, the invention pertains to improved polyethylene terephthalate blends derived from recycling of PET bottles.

BACKGROUND OF THE INVENTION

A major source of polyester, such as polyethylene terephthalate (PET), is the recycle of bottles made therefrom. These bottles conventionally are prepared from a polyethylene terephthalate resin with a base overlay cup of high density polyethylene (HDPE) resin. Paper labels, etc. are utilized.

The usual separation plant, such as described in Modern Plastics, Apr. 1980 page 82-3 crushes the received material, grinds it, and separates fines and paper labels through such as fluidized-bed separation procedures. The remaining materials primarily are polyethylene and polyethylele terephthalate. Further separatory procedures are employed to obtain these two materials as separate streams for individual recycle and reuse.

Recently, a foamed polystyrene wrap-around label has been applied to the PET body. This presents an additional problem, now adding a third major different polymer component to be separated.

Another problem experienced in the reuse of polyesters, whether obtained from PET bottle recycling or other, has been the fact that the thermoplastic polyesters are subject to hydrolysis in the presence of moisture when in the molten state during (re)processing. This hydrolysis results in a marked decrease in molecular weight, which then is reflected by marked lowering of physical properties, particularly toughness. To prevent hydrolysis during (re)processing, it has been necessary to dry the polyester to a moisture content of less than such as about 0.005 weight percent or less, a difficult procedure without deteriorating the polyester.

Needed are improved methods of reuse of the tremendous quantities of PET available in the form of recycle material. This material is either from recycle of the tremendous use of PET bottles, or from scrap in primary polyester bottle forming and other purposes. Just for example, the above referred to Modern Plastics article indicated an estimated 1.5 billion PET soft-drink bottles shipped during 1979 accounting for an approximate total of 150000 metric tons of resin in that single usage. In the intervening time, this likely has doubled; presenting a large potential area for useful recycle. Additionally, probably equivalent quantities of PET are used elsewhere in many other applications presenting equivalent opportunities for recycle.

Brief Summary of the Invention

I have solved many of the problems in reusing polyesters. My invention is based on a blend of (a) a polyester and (c) a desiccant.

(A) By blending (a) the polyester with (b) a block copolymer of a conjugated diene with a monovinylarene, and (c) a desiccant selected from calcium, magnesium, strontium, barium, or aluminum oxides, I am able to produce a tough pliable product without the necessity of any drying, retaining essentially the effective properties of the polyester.

(B) In a further aspect of my invention, I blend (a) polyester, (b) the aforesaid block copolymer of a conjugated diene with a monovinylarene, (c) the aforesaid desiccant, further with (d) a poly(mono-olefin) such as high density polyethylene. This produces a tough, pliable product, with useful impact strength and elongation for injection molding, well suited as a substitute for impact polystyrene, for example.

(C) In another embodiment of my invention, I blend (a) polyester, (b) the block copolymer of a conjugated diene with a monovinylarene, (c) the desiccant, (d) the polymono-1-olefin, preferably high density polyethylene, and (e) a polymonovinylarene, preferably polystyrene. In accordance with this aspect of my invention, the product is a tough, pliable product, suitable for molding of high impact parts. The product can be prepared from blending, such as by grinding together, a PET bottle including the base cup and polystyrene label, supplementing with such added components as necessary for a blended product, and including my important additive the conjugated diene/monovinylarene block copolymer.

(D) In a further embodiment of my invention, I blend (a) the polyester, (d) the poly(mono-1-olefin), and the (c) desiccant.

In related aspects of any of the above, I further use (f) an oil, preferably a light mineral process oil.

DETAILED DESCRIPTION OF THE INVENTION

(a) Polyester

The (a) component is any of the polyesters known as polyester resins. These are described in detail in such as the Condensed Chemical Dictionary, 7th Edition, by Rose and Rose, pages 758-759 (Reinhold, New York, 1966). These polyesters also are described in such as Block Copolymers by Allport and Janes (John Wiley, 1973) pages 264 and following. Polyesters are prepared by esterification procedures, alcoholysis, acidolysis, ester-ester interchange, or reaction of acid chloride with alcohol, as described in many publications. Primary preparation, commercially, of course, is by esterification reaction of a polyol with a polyacid. Most important of the polyester resins are those designated as the polyalkylene terephthalates.

Particular types include such as polyethylene terephthalate, polypropylene terephthalate, polybutadiene terephthalate, and various blends of the polyalkylene terephthalates or reaction products of a mixture of reactants. Most important commercially at present are the polyethylene terephthalates (PET), having a density of the order of about 1.34 to 1.39 g/cc, commonly employed in the PET beverage bottles.

(b) Conjugated Diene Monovinylarene Block Copolymers

The (b) component is a block copolymer of a conjugated diene with a monovinylarene, with a sufficient balance of cojugated diene:monovinylarene to be designated as a thermoplastic of rubbery (elastomeric) character. These block copolymers can be depicted by the formula (AB).sub.n Y wherein A and B respectively represent segments or blocks of polymonovinylarene (polymonovinyl-substituted aromatic compound), and polyconjugated diene, and wherein Y is a residue of a polyfunctional initiator or a polyfunctional coupling agent. The block copolymers can be prepared either by polymerization procedures effective to prepare a linear block structure, or by sequential polymerization procedures with coupling, all as is well known in the art.

Suitable conjugated dienes are the hydrocarbon conjugated dienes used alone or in admixture, and containing of the order of 4 to 12 carbon atoms per molecule, more usually 4 to 8 carbon atoms per molecule, including such as 13-butadiene and isoprene, both of these presently being preferred, as well as such as 23-dimethyl-13-butadiene, piperylene, 3-butyl-13-octadiene, and the like.

Among the suitable monovinylarenes are those of 8 to 18 carbon atoms per molecule, such as the presently preferred styrene, as well as 3-methylstyrene, 4-n-propylstyrene, 4-cyclohexylstyrene, 4-decylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, the vinyl naphthalenes, and the like, alone or in admixture.

Among the presently preferred block copolymers are such as the butadiene/styrene block copolymers, in which the blocks can be homopolymeric, or tapered, isoprene/styrene block copolymers of similar nature, butadiene/styrene/vinyltoluene random block terpolymers, and other terpolymers such as the butadiene/styrene/alpha-methylstyrene block terpolymers. Most preferably the block copolymer will have a weight ratio of about 50:50 conjugated diene:monovinylarene copolymerized to 75:25 presently preferred about 60:40.

(d) Desiccant

The (c) component is a desiccant capable of absorbing or reacting with water, and is a desiccated component selected from the group consisting of calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide, partially hydrated aluminum oxide. Presently preferred is desiccated calcium oxide.

Presently preferred and available commercially is an admixture of either about 90 weight percent or 80 weight percent desiccated calcium oxide and correspondingly 10 or 20 weight of a light mineral process oil employed both to provide a convenient means of handling the desiccated calcium oxide in effectively powdery, yet easily flowing form, as well as protection of the desiccated calcium oxide from absorbing moisture, thus providing an easily dispersible form of the calcium oxide in polymers.

(d) Poly(mono-1-olefin)

The (d) component is a poly(mono-1-olefin), such as and presently particularly preferred a high density or low density polyethylene, most preferably high density polyethylene. Other poly(mono-1-olefin)s employable are the normally solid polypropylene, polybutylene, polyisobutylene, poly(1-pentene), ethylene/butylene copolymers, ethylene/1-hexene copolymers, and various blends thereof.

It should be noted that the term "polyethylene" in the industry has come to include a variety of copolymers in which several significant percents of butylene, isobutylene, or 1-hexane, are included in the generalized term "polyethylene".

Presently most preferred because of its use as a protective lower cup exteriorly on PET bottles is a high density polyethylene, of a density of about 0.93 to 0.97 g/cc.

(e) Poly(monovinylarene)

The (e) component is a poly(monovinylarene) (poly(monovinyl-substituted aromatic compound) based on hydrocarbon monovinylarenes. These are normally solid, resinous materials, well known in the art. Presently preferred are the commercially available polystyrenes. Alternatively, useful and suitable materials include such as poly(alpha-methylstyrene), poly(vinyltoluene), and various blends thereof. Particularly useful commercial polystyrenes are those having a density of about 1.03 g/cc and a melt flow of such as about 2.5 g/10 min. However, any of the poly(monovinylarenes) prepared from the monovinylarenes as detailed above are usable. Many of the poly(monovinylarenes) may contain as copolymerized component other ethylenically saturated compounds such as alpha-methylstyrene, acrylonitrile, methacrylates, and the like.

(f) Light Mineral Oil

The light mineral oil is an optional but desirable component in any of my blends. A suitable light mineral oil is described as a primarily paraffic and naphthenic oil derived from crude oil, coal, oil shale and the like, having an aromatic content of about 10 to 49 percent by weight, a specific gravity of about 0.85 to 0.95 a flash point of about 300.degree. F. to 600.degree. F., and a viscosity at 100.degree. F. of about 60 to 3500 SUS.

COMPOSITIONS

In my blends, any suitable and effective proportions can be used. The percentages given below are recommended for most purposes, but it should be recognized that blends suitable for various applications can be made outside of the designated ranges.

It is recognized that the percentages in total may total greater than one hundred percent, but since the composition is limited to 100 percent, an increase in one component then is balanced by a decrease in one or more other components.

In my composition (A) of (a) polyester, (b) rubbery block copolymer, and (c) a desiccant, my inventive terblends are chosen in proportion so as to provide high impact strength, acceptable tensile properties, and hardness. Presently preferred are weight percentages of such as (a) about 50 to 90 weight percent polyester, more preferably about 70 to 85 weight percent; (b) about 5 to 40 weight percent rubbery block copolymer, more preferably about 10 to 20 weight percent; (c) about 3 to 20 weight percent of the designated desiccant, more preferably about 5 to 10 weight percent; and optionally (f) about 0.5 to 5 preferably about 1 to 2 weight percent of the light mineral oil.

In the embodiment of my invention (B) employing the (a) polyester, the (b) rubbery block copolymer, (c) the desiccant, and (d) a poly(mono-1-olefin), the proportions preferably should be in order of (a) about 50 to 90 weight percent polyester, more preferably about 60 to 80 weight percent; (b) about 3 to 30 weight percent of the rubbery block copolymer, more preferably about 10 to 20 weight percent; (c) about 3 to 20 weight percent of the aforesaid desiccant, more preferably about 5 to 10 weight percent; (d) about 3 to 25 weight percent of the poly(mono-1-olefin), more preferably about 5 to 10 weight percent; and, optionally (f) the light mineral oil in the amount described above, about 0.5 to 5 preferably about 1-2 weight percent.

In the further embodiment (C) including (e) a polymonovinylarene, presently suggested weight percents are of the order of (a) about 25 to 75 weight percent polyester, more preferably about 35 to 50 weight percent; (b) about 3 to 30 weight percent rubbery block copolymer, more preferably about 10 to 20 weight percent; (c) about 3 to 20 weight percent desiccant, more preferably about 10 to 20 weight percent; (d) about 10 to 35 weight percent poly(mono-1-olefin), more preferably about 20 to 25 weight percent, and (e) about 3 to 20 weight percent polymonovinylarene, more preferably about 5 to 10 weight percent; and optionally (f) about 0.5 to 5 preferably about 1 to 2 weight percent of the light mineral oil.

In my blend embodiment (D) including (a) a polyester, (d) the poly(mono-1-olefin), and (c) and the dessicant, the presently suggested weight percents are of the order of (a) about 50 to 90 more preferably about 80 to 90 weight percent; (d) about 3 to 20 preferably about 5 to 10 weight percent; and (c) about 3 to 20 preferably about 5 to 10 weight percent; and optionally (f) about 0.5 to 5 preferably about 1 to 2 weight percent.

Blending

My blends can be prepared, in any of the embodiments, by any conventional and suitable means for combining such ingredients, such as solution blending, milling, batch mixing, continuous extrusion, and the like.

The blends, of course, can contain conventional additives such as antioxidants, UV stabilizers, pigments, fillers, flame retardants, and the like, as in known in the arts. The percentages of materials employed in the suggested and preferred blends are based on the weight of the total polymeric ingredients plus desiccant, plus, where used, oil. These weights are exclusive of any of the other additives.

Preferably, my blends are prepared recycled PET beverage bottles, and effectively eliminate the need for separating bottles, base cups, polystyrene labels, so-forth, before grinding. The blends can be prepared by dry blending, followed by subsequent extrusion at suitable melt temperatures into strands, cooling, cutting into pellets, and the like.

My blends can be molded by known molding processes, such as injection molding, into useful high impact resistant articles such as trays, containers, automotive parts, and the like.

Most usefully, when applied to the present PET composite bottles, I produce a useful product therefrom, and save considerable effort, work, and energy requirements otherwise presently consumed in present effects to separate the individual components into individual recycle streams for individual applications.


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