FLAME RETARDANT, ANTISTATIC THERMOPLASTIC

Abstract: A thermoplastic having both flame retardant and antistatic properties and a method for making same. The thermoplastic can be extruded into films or blown into foam. The thermoplastic can be used in a number of applications such as packaging for sensitive equipment, metal coating, temporary sheeting in nuclear and electronic industry.

Description: FLAME RETARDANT, ANTISTATIC THERMOPLASTIC BACKGROUND AND SUMMARY OF THE INVENTION Thermoplastics have been made separately with antistatic and flame retardant properties. This inven¬ tion combines both properties into one thermoplastic and the method for preparing the thermoplastic. The flame retardants and antistatic compounds are known in the art. There has been difficulty in combining the two into one thermoplastic compound. The benefits of an antistatic and flame retardant thermoplastic are that one film, foam or other final embodiment can be used instead of a dual system. The thermoplastic of this invention can be processed into any form as long as processing temperatures are below 450°F. Films can be extruded, co-extruded with other thermoplastic layers and laminated with or without reinforcing layers. The product can be blown into a foam. The thermoplastic of this invention can be used in a variety of ways. For example, sheeting can be made for temporary wall structures and floor insulation in the nuclear industry. The sheeting can also be used in the computer maintenance area to drape and floor work surfaces. In addition, the flame retardant and antista¬ tic thermoplastic is well suited for packaging and shipping needs. The thermoplastic can be used in a sheet for wrapping and as filler to protect equipment sensitive to an electronic charge. The flame retardant qualities are additional protection from hazards to the contents of wrapped or filled packaging. Another application is for thermoplastic coating of wires or pipe to be protected from electronic charges and fire damage. The thermoplastic can be used in many applica¬ tions and it is not intended to define the uses by this description but to give useful examples of the inven¬ tion. The thermoplastic of this invention is made of conventional thermoplastic resins which are dried at 165°F to 250°F with or without a desiccant so that they contain about 0.1% or less water. The antistatic agent is a nontoxic amide which is typically contained in a thermoplastic resin for mixing purposes. The flame retardant is similarly contained in a resin for mixing purposes and is an antimony oxide and organic halogen. The composition also contains an effective amount of hindered phenol and phosphite stabilizer package or bisphenol polyphenol antioxidants. The dried components are thoroughly mixed. The product may be processed in any manner compatible for thermoplastic up to temperature range of 450°F. The composition may be extruded, co-extruded with two layers of the same composition or another layer of thermoplas¬ tic, laminated with any type of film. The film lami¬ nates may be reinforced. A blowing agent can be added to the composition and a flame retardant and antistatic foam will be produced. DETAILED DESCRIPTION OF THE INVENTION The thermoplastic chosen for this invention can be any type including but not limited to polyethylene of any density or form such as high density or linear low density polyethylene, poly- propylene of copolymers or homopolymers, ethylene vinyl acetate, ethylene methacry- lic acid and mixtures thereof. The thermoplastic is chosen considering factors such as cost, strength, stiffness and final product configuration in the parti¬ cular application. All the ingredients including the thermoplastic resin are dried prior to mixing to reduce the water content to 0.1% or less by weight. The drying can take place in an oven with or without a desiccant such as granular calcium sulfate. The components are typically dried at 165°F for three hours. The drying range can go up to 250°F. The temperature and length of drying time is dependent on the achievement of the 0.1% water content. The other ingredients are effective amounts of flame retardant, antistatic agent and antioxidant. These additives are commercially available in resins. The resin containing the additive promotes uniform mixing with the thermoplastic. The flame retardant, antistatic agent and antioxidant are dried as described above for the thermoplastic. All the ingredients contain 0.1% or less water prior to mixing. The antistatic compound is a nontoxic amide. The commercially available additive is 5% nontoxic amide in a low density polyethylene manufactured as Statcease CD by Techmer Corporation. The Statcease product with 5% active ingredient can be used in a 5% to 65% range in the composition of this invention. The flame retardant is antimony oxide specifically antimony trioxide or antimony pentoxide and an organic halogen. A commercial product by Ampacet Corporation (Product Number 11371) includes effective amounts of antimony trioxide and decabromo- diphenyloxide in a linear low density polyethylene master batch. The antimony trioxide is 2% by weight and the organic halogen is 6% by weight in the final product. The fire retardant product is used in a range of 27% to 95% by weight of the final product. The final product contains at least 0.2% of an antioxidant hindered phenol and phosphite stabilizer package. A commercially available product is Ciba-Geigy Irganox 1010 which is added to the mixture. The starting materials can be mixed in any order of addition with the complete and thorough mixing after all the materials are added. The processing steps should not exceed 450°F. The thermoplastics of this invention are self extinguishing once the source of heat is removed and passes the UL V-2 test. The flame retardant properties were tested by the National Fire Protection Association procedure and passed the large-scale and small-scale test. The material also has static decay properties in compliance with U.S. Military Specification 81705B. The thermoplastic can be extruded to form a film. The product can be used as one layer of a multi-layer laminated film with the film of this invention making up at least one of the layers. Any type of adhesive can be used such as a pressure sensitive adhesive, acrylic, polyvinyl chloride, acrylonitrile, silicone, solvent, hot melt or rubber based. A flame retardant package of antimony trioxide and organic halogen is added to the adhesive such that the final content includes about 1.1% Sb_0, and about 5.6% organic halogen. EXAMPLE 1 A film was made of the following ingredients dried for 3 hours at 165°F: 48% low density polyethylene; 2% Irganox 1010; 35% Ampacet Product Number 11371; 15% Techmer Statcease. The materials were thoroughly mixed and extruded to form a film. EXAMPLE 2 Two films as described in Example 1 were used to make a 2-ply reinforced laminate. The adhesive was a solvent based acrylic with Sb 2 0-, organic halogen flame retardant additive. The adhesive is coated at 1 mil dry thickness. The adhesive layer holds into place a nonwoven reinforcing filament grid. A typical adhesive formula is shown in Table 1 which includes the volatile starting materials. After the adhesive dries, higher percentages of the flame retardant compounds are pre¬ sent. On one film coated with adhesive a nylon multifilament 460 denier with a Z twist is laid out in a diamond pattern grid. The grid is formed by filaments in two substantially parallel sets laid at 45° angles. The strands are laid out and spaced about 0.5 inches apart. The two thicknesses of film with the adhesive and reinforcing grid in between are passed between pressure rollers to form the laminate. TABLE 1 Fire Retardant Adhesive Formula Hexane 16.72% Ethyl Acetate 26.05% Antimony Oxide 0.65% Organic Bromine 3.24% Acrylic Concentrate 53.34% EXAMPLE 3 The film as described in Example 1 or the rein¬ forced laminate as in Example 2 may be coated with a pressure sensitive adhesive to form a pressure sensitive tape. The adhesive may be a solvent based acrylic deposited at 30 lbs. per ream application weight. The adhesive may be applied by direct gravure or roll transfer coating. A release paper is provided. EXAMPLE 4 The film as described in Example 1 or the rein¬ forced laminate as in Example 2 may be coated with a hot melt adhesive to form a pressure sensitive tape. The adhesive is a rubber based hot melt adhesive commonly available from National Starch and Chemical Co. or Findley Adhesives, Inc. The adhesive is applied at a thickness of 6 mils to produce a permanent bonding tape. A release paper is provided. EXAMPLE 5 The thermoplastic as described may be mixed with a typical blowing agent of a chlorofluorocarbon such as Genetron 12 manufactured by Allied Signal Corp. and extruded into a foamed sheet. The blowing agent is injected into a molten phase of the thermoplastic material. The mixture is then forced through a die and upon the drop of pressure from inside the extruder to atmospheric pressures. The blowing agent expands to form a foamed sheet of density 6 to 8 lbs. per cubic foot.

Claims: AMENDED CLAIMS [received by the International Bureau on 31 October 1989 (31.10.89). original claims 1 and 6 amended; other claims unchanged (2 pages)] 1. A method for making a flame retardant and antistatic thermoplastic comprising the steps of: (a) drying the thermoplastic resin to reduce the water content to 0.1% or less by weight; (b) drying the fire retardant composition to reduce the water content to 0.1% or less by weight; (c) drying the antistatic composition to reduce the water content to 0.1% or less by weight; (d) drying the antioxidant to reduce the water content to 0.1% or less by weight? (e) mixing thoroughly the thermoplastic resin, fire retardant composition, antioxidant and antistatic composition; and (f) processing the mixture to process a final thermoplastic produced at temperatures below 450°F. 2. A method for making a flame retardant and antistatic thermoplastic of claim 1 wherein steps (a) , (b) , (c) and (d) the drying process is carried out until about 0.1% water or less by weight remaining in the resin, fire retardant composition, antioxidant and antistatic compositions and the drying temperature is between 165°F and 250°F. 3. A method for making a flame retardant and antistatic thermoplastic of claim 1 wherein steps (a) , (b) , (c) and (d) the drying process of the resin, fire retardant antioxidant and antistatic compositions is performed in the presence of a desiccant. 4. A method for making a flame retardant and antistatic thermoplastic of claim 1 wherein step (e) the mixture is extruded at process temperatures below 450°F. 5. A method for making a flame retardant and antistatic thermoplastic of claim 1 wherein during step e a blowing agent is added and the material is processed 6. A flame retardant and antistatic thermoplastic comprising: a thermoplastic with about 0.1% or less water content by weight; an antistatic compound of thermoplastic resin containing about 5% nontoxic amide with about 0.1% or less water content by weight; an effective amount of flame retardant with about 0.1% or less water content by weight; and a hindered phenol and phosphite antioxidant with about 0.1% or less water content at least 0.2% by weight of the final product. 7. A flame retardant and antistatic thermoplastic of claim 6 wherein said flame retardant compound is a thermoplastic resin containing about 2% antimony oxides and about 6% organic halogen. 8. A flame retardant and antistatic thermoplastic of claim 6 wherein the final product is an extruded thermoplastic film. 9. A flame retardant and antistatic thermoplastic of claim 6 wherein the final product is a co-extruded film of at least two film layers, at least one of said films having the composition of claim 6. 10. A flame retardant and antistatic thermoplastic wherein the final product is at least two layers of laminated film at least one of said films having the composition of claim 6 and the laminate adhesive has an effective amount of flame retardant. 11. A flame retardant and antistatic thermoplastic of claim 6 wherein the final product is at least two layers of laminated film at least one of said films having the composition of claim 6; laminate adhesive layer with an effective amount of flame retardant; and

Inventors: RAMSEY BOYD J, RAMSEY, BOYD, J.
Applicants: REEF IND INC, REEF INDUSTRIES, INC.
Application year: 1989
Main classification: C08K9
IPC codes: C08K9