WO1997042262A1 - Composition and process for high load coloring of plasticized resins - Google Patents

Abstract

A process for coloring plastic resin, comprised of forming a dispersion of pigment, plasticizer, and surfactant and mixing said dispersion into the resin.

Description

COMPOSITION AND PROCESS FOR HIGH LOAD COLORING OF PLASTICIZED RESINS

Background of the Invention

This invention relates to a process for high load coloring of resins which incorporate a plasticizer, particularly flexible polyvinyl chloride (PVC) , propionates, styrenics, etc. This invention also relates to a composition for coloring resins, particularly polyvinyl chloride. More particularly, this invention relates to a composition which functions as a combination flexibilizer and high load colorant for plasticized resins. The invention will be described with particular reference to PVC, however, the colorant composition and process are envisioned to function in concert with any resin which incorporates a plasticizer during processing.

In the production of polyvinyl chloride and articles formed therefrom, plasticizers have long been used to achieve a high degree of flexibility. In general, it is believed that plasticizers influence the secondary valences or van der Waals forces which act between polymer chains and the stearic flexibility of individual chains which depend essentially on the structure of the polymer itself. Accordingly, a great deal of work has been performed in developing plasticizer compositions which are efficient, highly dispersable, and long lasting.

For example, United States Patent 3,892,692, herein incorporated by reference, describes a vinyl chloride-ethylene copolymer which is flexibilized by the addition of between about 15 and about 30% by weight of a plasticizer selected from the group consisting of dialkyl phthalates, dialkyl alkanedicarboxylates, and aryl and alkyl phosphates. In addition, the patent indicates that pigments commonly employed with vinyl chloride polymer compositions can be used. However, no details are provided regarding the coloring procedure, indicating that the colorant is added only by the traditional method of adding low levels of colorant during the mixing of the plasticizer into the PVC resin, or thereafter. Importantly, the present inventor has found that such a traditional coloring process cannot achieve a colorant load exceeding twenty percent (20%) without significant adverse effects. Particularly, exceeding this level in the traditional coloring process leads to agglomeration of colorant particles and inferior coloration. More particularly, in "critical applications", such as medical and optical clarity films, the colored resin can demonstrate less transparency, less color-strength, and less tint strength. Similarly, United States Patent 4,207,225, herein incorporated by reference, discloses a plasticizing composition for polyvinyl chloride resins. The plasticizer composition is a combination of an alkyl diphenyl phosphate and a tris(alkoxyalkyl) phosphate. Interestingly, the effectiveness of the plasticizing composition in blending with the polyvinyl chloride resin is evaluated by extruding the mixture in combination with a dye—added to the plasticized PVC. The residual color that adheres to the roller surfaces evidences the level of compatibility between the flexibilizer system and the PVC resin.

United States Patent 4,358,499, herein incorporated by reference, discloses a process for forming a flexible PVC roofing membrane. The process comprises mixing a PVC resin with a plasticizer, an emulsifier, a filler, heat, U.V. and processing stabilizers, and pigment. Again, the pigment is added at the time the plasticizer is added or after and is present at only very low levels, i.e. 10 parts per hundred parts of resin. United States Patent 4,390,585, herein incorporated by reference, discloses a plasticizing agent for PVC resin which is selected from trimellitate esters. As explained therein, there are a variety of known PVC plasticizing agents such as phthalates, phosphates, dibasic acid esters, epoxies, benzoates, citrates, isophthalates, pentaerythritol esters, glycolates, polyester, chlorinated hydrocarbons, cross-linkable polymers and the like including the preferred trimellitate esters. However, colorant is added only at low levels and is added while blending the ingredients to form the overall composition according to traditional PVC processing techniques.

Similarly, United States Patents 4,577,998 and 5,191,007 herein incorporated by reference, disclose flexible polyvinyl chloride compositions including pigmentation, however, the pigmentation is simply added at conventional levels as an ingredient blended with the overall composition.

It has been found that the traditional PVC coloring procedure relied on in the above discussed patents does not allow high loading of pigments. Since there is increasing desire in the art to achieve the depth of color associated with high pigment loading, efforts have been expanded to achieve higher loading.

In this regard, compounders who recognize the shortcomings of traditional coloring procedures yet desire high pigment loads in flexible PVC, often utilize a flushing process. The flushing process requires forming pigment into a presscake comprised of pigment at its primary particle size and water. Typically the presscake is then "flushed" with heated wax under pressure to displace the water and achieve dispersion of the colorant in the PVC. Although the flushing technique can achieve color loads as high as fifty percent (50%) , typical flushes are manufactured of waxes including polyethylene or polypropylene wax which may have a negative influence on the flexible PVC. In addition, flushing procedures require additional equipment, high energy expenditure, and extra processing steps. Clearly, the expense associated with presscake coloring is undesirable to compounders.

However, when compounders attempt to color flexible PVC with high loads of dry pigment, unacceptable particle agglomeration occurs. This agglomeration is unacceptable because color strength, transparency, physical properties, shading, and ultimate processability by the end user are effected by the agglomeration. Accordingly, prior to the present invention, presscake flushing has provided the best available option to achieve high-load coloring.

In an attempt to eliminate a reliance on the complexity and expense of flushing and still obtain high pigment loading, the present inventor has developed a process which allows production of high pigment loaded resins, particularly flexible polyvinyl chloride.

Summary of the Invention

Accordingly, it is a primary object of this invention to provide a new and improved process for coloring resins with high pigment loads.

It is an advantage of the invention to provide superior coloring of flexible polyvinyl chloride.

It is a further object of this invention to provide a new and improved composition for simultaneously coloring and plasticizing resins, particularly polyvinyl chloride.

To achieve the foregoing objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the process of this invention comprises dispersing a colorant into a plasticizer, preferably with the aid of a surfactant, to achieve a high grade dispersion at of least 20 to 80% pigment. Thereafter, the colorant/plasticizer dispersion is mixed with a resin to produce a high colorant loaded composition. Preferably this composition contains at least twenty percent 20% by weight colorant. More preferably, the composition contains at least 30% by weight colorant. The process has been found particularly effective in coloring flexible polyvinyl chloride resins. In a preferred procedure, the plasticizer/colorant dispersion is comprised of between 20 and 80% by weight plasticizer, between 0 and 40% by weight surfactant, and between 20 and 80% by weight colorant. In a particularly preferred form of the invention, the dispersion is comprised of between 40 and 70% by weight colorant, between 30 and 60% by weight plasticizer and from greater than 0 to about 25% by weight surfactant.

In a preferred form of the invention, the plasticizer is selected from the group consisting of diisonoyl phthalate, dioctyl adipate, dioctyl teryl n- phthalate, dioctyl phthalate, dioctyl teryl phthalate and mixtures thereof; the surfactant is selected from the group consisting of STO, SMO, Tergitol and mixtures thereof; and the colorant is selected from organic and inorganic colorants, pigments, fillers and dyes.

Detailed Description of the Preferred Embodiment

An organic pigment which may be selected from the group identified above, is blended into a mixture of a plasticizer and a surfactant by the slow addition of the pigment. Preferably, the plasticizer/surfactant mixture is comprised of between 60 and 100% by weight plasticizer and between 0 and 40% by weight surfactant.

In a preferred embodiment, sufficient colorant is added to achieve a final plasticizer/colorant dispersion having between 20 and 80% by weight colorant. After a suitable plasticizer/colorant dispersion is achieved, the dispersion is preferably further dispersed via a mechanical method such as a media mill or roll mill to achieve the preferred particle size and requisite dispersion for the application. However, for non-critical applications an adequate particle dispersion may exist without further milling. In contrast, for critical applications, the slurry of plasticizer, colorant and surfactant must be further sheared to achieve the desired particle size.

After milling, a very high grade dispersion of a highly loaded colorant in a plasticizer base exists which can then be stored or used immediately to produce the final product of a highly loaded resin, for example flexible PVC. Particularly, the plasticizer/colorant composition is mixed into a PVC resin using a high speed mixer. Thereafter the colored PVC composition can be placed into an extruder and pelletized for later molding or other processing as desired and common in the art.

Examples The compositions of Table 1 were prepared according to the following procedure. First, the surfactant and plasticizer were combined in a Shar Inc. Model D-20SH mixer. The pigments were then dispersed into the plasticizer/surfactant mixture by slow addition and mixed for 10 minutes at 80°F. The dispersions were then subjected to further shear in a three roll mill until the entire slurry mixture had been passed.

The resin compositions were then formed in the proportion of Table 2. PVC resin (5265 from VISTA) was loaded into a Henschel mixer and mixed at high speed to 180°F until a temperature of 180°F was achieved. The dispersions of Table 1 were then added to the resin in conjunction with stabilizers (777 Altastab and 1456 Synpron) and mixed on high to 205°F. A lube pack (18.19% CaSt; 45.46% PA101 Cure Ace; 36.35% AC 316 APE wax) was added and the composition was again mixed on high to 210°F. TABLE 1

TABLE 2

Evaluation of the colored resin compositions was performed by extruding the colored PVC compositions on a single screw extruder and pelletizing. Visual inspection thereof revealed each flexible PVC composition to have excellent color strength, transparency, development and dispersion.

Thus, it is apparent that there has been provided, in accordance with the invention, a process that fully satisfies the objects, and the advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to all such alternatives, modifications and variations as they fall within the spirit and broad scope of the appended claims.

Claims

In the Claims :

1. A process for coloring a resin comprised of forming a dispersion of colorant, plasticizer, and optionally a surfactant and mixing said dispersion into said resin to form a colored compound.

2. The process of claim l wherein said dispersion is comprised of between about 20 and 80% by weight colorant.

3. The process of claim 2 wherein said dispersion is comprised of between about 20 and 80% by weight plasticizer and between about 0 and 40% by weight surfactant.

4. The process of claim 3 wherein said dispersion is comprised of between about 30 and 50% by weight colorant, 50 and 70% by weight plasticizer, and at least an effective amount of surfactant.

5. The process of claim 1 wherein said plasticizer is selected from the group consisting of diisononyl phthalate, dioctyl adipate, dioctyl teryl n-phthalate, dioctyl phthalate, dioctyl teryl phthalate.

6. The process of claim 1 wherein said surfactant is selected from the group consisting of sorbitan fatty acid esters, fatty amides, polyoxyethylene sorbitol esters, sulfated fatty esters, sorbitol esters, alkoxylated esters and mixtures thereof.

7. The process of claim 1 wherein said colorant is selected from the group consisting of organic pigments, inorganic pigments, dyes, fillers and mixtures thereof.

8. The process of claim 1 wherein said resin is polyvinyl chloride.

9. The process of claim 1 wherein said colored compound is comprised of at least 20% by weight colorant.

10. A composition for coloring polymeric resinous materials comprised of about 20 to 80% by weight colorant dispersed in between about 20 to 80% by weight plasticizer and about 0 to 40% by weight surfactant.

11. The process of claim 10 wherein said dispersion is comprised of between about 30 and 50% by weight colorant, 50 and 70% by weight plasticizer, and at least an effective amount of surfactant.

12. The process of claim 10 wherein said plasticizer is selected from the group consisting of diisononyl phthalate, dioctyl adipate, dioctyl teryl n-phthalate, dioctyl phthalate, dioctyl teryl phthalate.

13. The process of claim 10 wherein said surfactant is selected from the group consisting of sorbitan fatty acid esters, fatty amides, polyoxyethylene sorbitol esters, sulfated fatty esters, sorbitol esters, alkoxylated esters and mixtures thereof.

14. The process of claim 10 wherein said colorant is selected from the group consisting of organic pigments, inorganic pigments, dyes, fillers and mixtures thereof.

15. The process of claim 10 wherein said resinous material is polyvinyl chloride.