IL26168A - Molded articles and process for their manufacture - Google Patents

Description

Patents Form No . 3 PATENTS AND DESIGNS ORDINANCE.

SPECIFICATION.

"MOLDED ARTICLES AM) PROCESS FOR THEIR MAMJFACTURE" «on»*«srt? I' nm ο» ¾ιχο o sno" ' A THUii HUOH ROBE S a United States ci of 4208 Eas ern to^^ States f merica^ do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement : .- k flexible, cpoxy resin co ting: i.~ / an illustration of a continuous ancillary reinforcing element. A flexible polyester resin coating is another illustration.

These are advantageously applied in a liquid state to coat the entire interior surface of the joint cavity. jRlgid cellular ; plastics, e.g., igid polyurethane foams, illustrate suitable ■ materials to provide an ancillary reinforcing element complete-'. ly filling the joint cavity.

I A large number of plastics materials are suitable to i i form the shell. Preferred plastics comprise plasticlzed poly- • vinyl chloride, copolymers of vinyl chloride in a plasticlzed state, and polymers of' ethylene. he polymers containing vinyl : chloride in a polymerized state are advantageously applied as ■' nlastlsols . j * i Plastisols are a very suitable material with which to j form the shell of the composite article of this invention.

Plastisols, their formulation, and application methods are well described in the literature. For convenience and brevity, ref erence Is made to: (a) Modern Plastics 26, 78 (April 19^ ). (b) ' Geon Resin 121 in Plastisol Compounding.

Service ^Bulletin PR-4, Revised October I958, '' B. F. Goodrich Chemical Company, '24 pages. (c)" The"Vanderbilt News, Vol. 26, No. 3, ' \ June "i960.· R. T. Vanderbilt Company, \ Inc., Page 12. (d) Modern Plastics Encyclopedia, Issue for I96I, 'published in September i960. Vinyl polymers and copolymers. Pages 129 to 132, Plastisol Molding, pages 765 to 771. (e) Modern Plastics Encyclopedia, 1965 (issued in 196 ) . Vinyl Polymers and Copolymers, page 271. Plastisol Molding, page 690.

Plastisols are dispersions of finely divided polyvinyl resin powders in liquid organic plasticizers . The resins con- Jily , tain predominantly polyvinyl chloride v/ith or without some other Ί υo polymerised monomer. The dispersions are usually of creamy consistency at room temperature and are alv/ays fluid to at least a certain degree. Dioctyl phthalate, dioctyl adipate and poly- ket, consisting of a mixture of a vinyl dispersion resin and a reactive monomer. The former is dispersed in the latter. "When heat is applied to this system, it causes gelation and fusion '.. ...V:.. ■ and polymerizes the reactive monomer, thereby producing a more rigid product than previously produced with conventional plastisols. Reactive acrylic monomers are examples of such reactive monomers. Such reactive vinyl plastisol systems are suitable for forming the shell of this invention.

' -When molding plastisols, the material is heated to a gelling temperature and a gelled film or layer is formed which is very weak and cheesy, but which does not flow. Further heat - ing is required to "fuse" the deposit, causing the resin to dissolve in the plasticizer and form a tough homogenous resinous mass in which the powdered resin and liquid plasticizer have formed a single uniform phase. The fusion transforms the cheesy deposit or film to a tough leather-like homogenous shell.

The temperatures required vary from composition to composition and also var with time, but all these are well / «' known In the art. There are three types of temperatures in- I volved: (l) oven temperature, (2) mold (die) temperature, and I I (3) temperature of the plastlsol. Gelation temperature may be i , · . ! accomplished by heating the oven from 150 to 600°F. and usually is between a plastlsol temperature of 150 to 300°F. The necessary time varies with the temperature used. Fusion is accom- ' plished by heating the gelled layer in ovens from about 350°F. to I about 650°F. The achieved plastlsol temperature for fusion r* ' of time the mold Is exposed to the temperature. of gelation. The excess plastisol is then removed by pouring off the liquid portion. Heating is then continued to complete the fusion and the ■r molded shell is then removed or stripped from the mold. There' are two methods known in slush molding: (i) One Pour Method, and (il) Two Pour Method. Both are well known in the art and are applicable to make the shells of this invention from plas- tlsols.

Rotational molding is another method of casting, its basic departure from slush molding is that, instead of an excess of the liquid plastisol, a premeasured quantity of the fluid is used when charging the mold. This eliminates 'the need for removing any excess. As the mold containing the charged fluid plastisol is rotated on the rotational molding machine and the mold is heated, gelation of the plastisol occurs uniformly on the inner surface of the heated mold. By continuing the heating and/or increasing the temperature of the mold, the gelled plastisol fuses. The fusion completes the molding of the shell and the completed shell is then stripped and removed from the mold.

Whereas the casting by slush molding or rotational molding is preferred to form the shell from plastisols, other methods known in the art may also be followed to achieve the same purpose.

The shell components may be formed of other materials such as vulcanized natural rubber or synthetic rubber. These shells may be formed according to known procedures of rubber^ technology. One of the methods useful in preparing shells \ from rubber is to use latex molding (latex casting) compounds, utilizing plaster of paris molds. The Vanderbilt News, Vol. 27, Mo. 4, December 1961. page 72, deals with latex compounding which can be used to make shells for the composite articles of the present invention.

Other suitable plastics materials which can form the shell components of this invention are illustrated by methyl methacrylate polymer, ethyicellulose, polycarbonates, poly-urethane elastomers, flexible epoxy compounds, flexible polyesters, amongst others. On some of these, some additional data may be useful and is given below: In preparing methyl methacrylate shells, a mixture was prepared of methyl methacrylate monomer, polymethylmethacrylate (DuPont's Lucite "30"), benzoyl peroxide, a white color paste compatible with methyl methacrylate and dimethyl -p-toluidine . The shells were cast into suitable molds, e.g., a latex mold. Polymerization occurs at room temperature and. heating to 100-12G°F. accelerates polymerization considerably. A suitable thickness of shell was produced in three coats. The produced molded shell had acceptable flexibility and adequate mold surface reproduction. Plasticizers may be incorporated, such as primary, non-migrating saturated polyester plasticizers, compatible with methyl methacrylate monomer.

Polycarbonates can be cast from organic solvent solutions. Methylene chloride Is a suitable solvent. Lexan No-. 105 (General Electric Co. ) forms a solution in the proportion of 83.3^ of polycarbonate and 1β.7 of methylene chloride. All . parts and percentages in this application are by weight. Slush casting in latex molds illustrates a useful method. The latex molds are known in the art in casting plaster of parls objects. -Polycarbonates are polymeric combinations of bi-functional phenols or bisphenols, linked together through a carbonate linkage. They can also be blow molded and vacuum formed.

' \ A suitable flexible epoxy resin usually has three ingredients: (l) a low molecular weight epoxy resin of the ©pichlorhydrin-bisphenol A oondensation product type, like Shell Chemical's Epon 823; (2) a low viscosity liquid aliphatic polyepoxide, like Epon Resin 871, which imparts increased flexibility to Epon resin compositions; and (3) a curing agent, illustrated by diethylenetriamine and triethylenetetramine, respectively known as DTA and TETA. Other comparable items may replace the specific ones here mentioned. Fillers may be present. To regulate the viscosity of the mixture a submicroscopic pyrogenic silica prepared in hot gaseous environment can- be used. This is marketed by Cabot Corporation under the trade name of Cab-O-Sll. Shells can be molded in latex mold3 or other elastomer molds. These are actually multi-pieced plaster of paris mold3 externally reinforcing an entirely separate second flexible elastomer mold, having one opening for pouring in the composition to @ molded and set. The rubber surface is advantageously coated with a mold release agent and the epoxy composition is slush cast into the molds. The above discussed slit mold is used to mold shells showing undercuts. Other molds and molding methods can also be used depending on the article to be manufactured. Epoxy plasticlzers include epoxy compounds of fatty oils and their acids. Epoxy novolac resins and cycloaliphatic epoxles are other illustrative members of this group. Polyamids and acid anhydrides may also be used as curing agents.

Polyester resins are' usually made in two steps. In the first step, a condensation reaction is carried out between a dibasic acid and a diol, and this is then blended in a second step with a monomer. Maleic anhydride, fumaric acid and itaconic acid are examples of the . unsaturated dibasic acids.

Phthallc anhydride and isophthallc acid are modifying components in dibasic acid mixtures. Propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol and neopentyl glycol, are illustrations from a long list of glycols known to be suitable for formulating polyesters. Styrene and vinyl toluene illustrate crossllnking monomers. Flexible polyesters usually contain long chain acids or glycols. Laminae Polyester Resin EPX-126-3 of American Cyanamid is a suitable product to form shell components. ethylethyl ketone peroxide (ME peroxide) is a1 suitable crossllnking agent, and cobalt naphthenate accelerates the crosslinking. Compatible wax type compositions may be added to improve surface characteristics. Cab-O-Sil assists in regulat-' ing the thickness of deposit in slush casting. The desired shell thickness ma be achieved by two or three slush castings. Pro erties may be varied by blending rigid and flexible poly* esters. Latex molds and, in general, molds suitable for epoxy resins, may be used with polyesters.' Liquid urethane polymers, such as DuPont's Adiprene L-100, can be transformed into tough, rubbery solids by reaction of the isocyanate group with polyamlne or polyol compounds. In addition, some materials which do not contain active hydro- gens, such as the titanate esters, appear to catalyze crossllnking. Adiprene L-100 can be cured with diamines, or moisture (water), or polyols, ...or by catalysts, such as lead or cobalt ■ naphthenate, potassium acetate and titanate esters. Tetra- · ^ butyltitanate is an example of the esters. One of the popular polyamines is MOCA, which is ' -methylene-bls-( 2-chloro- ..; ■· - ... .· - aniline./)-.- A formulation is illustrated by 100 parts of Adiprene L-100 and 12. 5 parts of MOCA, which gives a MOCA ^-equivalent of 95 · Parts are by weight. Conditions were: mixing tempera- ture: 212°F., cure temperature : 212°F. , curing time: 3. hours .

LD- 20 is a different type of liquid urethane elastomer, which yields high quality vulcanizates when cured with MOCA. A respective formulation is illustrated by 100 weight parts of LD- 20 (DuPont) and 8. 8 weight parts of MOCA. This is mixed and . cured the same way as Adiprene L-100.. for the same length of f. · 10 time. It is improved by aftercuring 1 week at 75°F. at S relative humidity. In making a shell from these isocyanate elastomers, rotational molding is recommended. A silicone mold release is advantageously used to assist separation from the molds .

Ethylcellulose shells can be molded by vacuum forming and injection molding, as well as othe . methods . The same applies to cellulose acetate and cellulose acetobutyrate.. A. com-' bination of casting and hot melt methods may also be used, The preset molded shell can be prepared by various molding- processes . The selected process depends on the selected plastics material and on the shape and size of the shell to be molded. For illustrative purposes a few examples are given: Casting, such as slush casting or rotational casting, may be used with pia-s^eo^ flexible polyester, flexible epoxy 2 resins, methyl methacrylate, polycarbonates from solution, Injection molding or extrusion may be used with pia&k£&sty polycarbonates, ethyl cellulose, p©ly fehyien« July fS, j~ Vacuum forming may be used with polyethylene, poly- "196 carbonates , polyallome . plastisol or other plasticized polyvinyl chloride composition, polyethylene, etc. ! process also influences the mold selection. Plastisol illus¬ .invention and are included in the group of preferred shell forming . plastics . (l) a rigid composition comprising a filler bonded- by the elastomer solids of a latex; (2) a rigid cellular plastics; and (3) a, rigid synthetic resin composition comprising a rigid polyester resin or a rigid epoxy resin. These rigidifier groups will be discussed in further detail here below, (l) Rigid compositions comprising a filler bonded by the elastomer solids of a latex This group of rigldifiers is formed from a composition comprising (a) a binder, (b) a filler, (c) water, and in most instances (d) auxiliary materials required tu set the binder, or to stabilize the composition, or aid in dispersing the fillers.

The binders used are latices either of natural or of synthetic origin. The latex, as the term is used herein, is a water dispersion of an elastomer. In most cases the dispersed phase of the latices is a solid. Most synthetic latices are prepared by emulsion polymerization of the monomer or monomer mixture. Other synthetic latices may represent aqueous dispersions of elastomers, which have been obtained by other polymerization means, prior to emulsification . The latices useful herein include emulsions where the dispersed binder is still in the liquid state. ... The -latex binds the fillers and forms with them a solid and rigid layer. Preferably and additionally it also provides adhesion between the inner surface of the shell and the rigidifier. During the formation of the rigidifier, the water .evaporates and the elastomer remains. The latex should have good wetting power for the fillers used in the formulation of the. rigidifier. Additional surface active agents can be added to increase wetting power or to stabilize the latex. A more concentrated latex is of advantage , providing it has good wetting qualities j as it requires less evaporation of water during" the setting period. Centrifuging, careful evaporation of part of the water, creaming and electro-decantation are some of the methods used to concentrate latices, A practical level of latex solids content may be illustrated by a range of from about 0$ to about 65 . In. some cases lower and higher solid contents may also be.used. Natural latex is. available with a range of solids of from about 3'0$ to about 75 .

The following latices are useful in the preparation of the rigidifier: Natural rubber latex, like centrifuged natural Hevea latex; Gutta percha latex; Balata latex; Styrenebutadlene copolymer latices of varying monomer ratios: Polyisopre e latex; Neoprene latex (polychloroprene latex); Butadiene -acrylonltrlle latices of varying monomer ratios; Butyl rubber latex; Polyvinyl chloride latices plasticized either internally or by pla3ticizer emulsion addition; Polyvinylidene chloride latex; Vinyl' chloride-acrylic copolymer latices; Ethylene-propylene copolymer latex, emulsified as a cement, after polymerization is completed; and. Acrylic copolymer latices made of various monomer mixtures ;"""" and others.

The expression "acrylic polymer" is used herein as a generic term which includes acrylic copolymers, i.e. polymers made of more than one acrylic monomer. An acrylic monomer is an acrylic type acid, its derivatives and substitution products . of the acids and its derivatives. The term "derivative" includes esters and nitriles. The term "acrylic type acid" is a polymerizable alpha-beta unsaturated monovinylidene carboxylic acid, such as acrylic and methacrylic acids and their halogen substitution products.

Prepolymerized elastomers, e.g., Neoprene, may be emulsified in the presence or absence of volatile organic wate-r-immiscible solvents to form latex-type binders.

"■'It- is possible to vulcanize natural rubber particles in dispersed state, i.e., in latex form. Upon drying such latex immediately forms strong vulcanized films.

The fillers of a latex bonded rigidifier may be varied. Pigments, like titanium dioxide, lithopone, zinc sulfide, zinc oxide, and others used in emulsion paint formulations, may be used. Extender pigments and coarse fillers may also be used. Various types of clays or Kaolins, calcium carbonate (natural or precipitated), such as whiting, and coarser materials, like flint (SiOg) can be utilized. A 60 mesh silica.... illustrates the coarser materials'. Talc and magnesium silicate, barium sulfate, colored pigments, like iron oxides, ochres, etc. may be used. Addition of small quantities of fibrous materials to the fillers may help to strengthen the rigidifier. Asbestos fibers and short staple fiberglass may be mentioned as examples.

Other examples of fillers are: shell flour, carbon black, diatomaceous earth, aluminum hydroxide, hydrated alumina, bauxite powder, magnesium carbonate, dolomite powder (calcium-magnesium carbonate ), mica, etc. For the coarse particle 'size component, vitreous rock of igneous origin may be used. With γ proper care, portland cement may be incorporated as a filler'.

Coarse fillers have greatly reduced surface area, compared with fine particle size fillers. Therefore, a coarse filler can be loaded into a latex mix in comparatively high p ■rroportion, without requiring additional binder content. The coarse fillers help to reduce the danger of cracking during drying and assist in decreasing shrinkage to a considerable ex tent.

When using clays as part of the filler, the soft . clays, like McNamee clay, are more advantageous than the hard clays, like Dixie clay.

Concerning the water component of the latex composi- tions, it is advantageous to have as low a water content as possible because the water has to be evaporated during" the man ufacturing process. The water content of the composition form ing the rlgldlfler may be from about 10 to about 26% of the total weight of the composition. In some cases., the water con tent may go up as high as 25%, or more.

The auxiliary material component of the latex compositions may be one or more of the following: Latex stabilizers, like Igepals. (These are alkylphenoxypoly(ethyleneoxy)-ethanols. Some are nonyl phenol condensation products with ethylene oxide.) Surface active agents to facilitate filler or pig-. ment dispersion. (Darvan 7 is illustrative. It is a sodium salt of a polyelectrolyte . ) Vulcanizing agents and/or vulcanizing activators.' (Sulfur and zinc oxide are illustrative.) Vulcanization accelerators. (Activated dithiocar- bamate, like.Setsit 51, is an example.) Antioxidants. (Styrenated phenol type antioxidant, like Agerite Spar, and mixtures of polybutylated bisphenol A, like Agerite Superlite, are examples.-) Plasticizers represent another group of auxiliary additives.

,, With this type of rigidifier, the thickness of the rigidifier ranges from about 10 mils to about 500 mils, and in most practical applications, its thickness is at least that of the' shell of the manufactured product. This thickness can b formed of a single coat or can be built up by a plurality of coats. Considering the latex solids as the elastomer content of the latex, a practical relationship is illustrated by a range of from about 200 weight parts to about 2000 weight parts of filler, preferably 300 to 1000, for each 100 weight parts of the elastomer binder. Generally speaking the compositions forming this type of rigidifier are highly loaded latex compositions, that is, they have comparatively high filler 'content. The particle size of the fillers, i.e., their total surface area, and the comparative flexibility and toughness of the used elastomer may require variations in the proper ratios. It is advantageous that in the total filler component of the rigidifier-forming composition the coarse particle size fillers represent more than 50 of the total fillers. A practical useful range of the coarse particle size fillers could be given as from about oo to about 70% of the total filler component. · This range is based on the assumption that the particle size of the coarse fillers is about βθ mesh. The proper proportions, would change, should the relationship of the particle sizes (diameters) and surface areas of the "coarses" to the "fines" vary.

Example 1 The following illustrates a useful latex composition, i.e'. , Hevea latex composition, for forming the rigidifier.

Dry Con¬ Wet tent in Dry hei ht wet weight Weight PART A % by Weight Water 8.64 . 10$ Aqueous KOH solution 0.53 o!o ' ' o!o6 60$ Aqueous zinc oxide dlspers l 0.26 0.16 0.19 25$ Aqueous Darvan'7 solution 0.77 0.19' 0.22 68$ Aqueous sulfur dispersion 0.11 O.O7 0.08 McNamee Clay (Kaolin) 8.32 8.32 9.75' Yorkshire Whiting 24.87 24.87 2 .14 Subtotal for Part A 3.50 33.66 39.44 PART B Natural centrifug'ed latex, 62.5$ N.V.* 11.75 7.34 8.6Ο 10$ Aqueous KOH solution Ο.36 0.04 O.O5 25$ Aqueous Darvan 7 solution 0.07 0.02 0.02· 5$ Aqueous dispersion of Agerite Spar 0.11- 0.07 0.08 Setslt 51 accelerator 100$ 0.11 0.11 0.13 Subtotal for Part B 12.40 7.58 8.88 PART C Mix Parts A + B = Subtotal .90 41.24 48.32 PART D Silica 60 me 44.10 44.10 51.68 Total 100.00 85.34 100.00 * N.V. « Non Volatile content.

Preferably, Parts A and B are first prepared separately and then 'they are mixed. Part D is added last.

The following table shows the analysis of the filler component of. the latex composition of Example 1.

TABLE 1 Surface $ in sur- $ in $ in in sq. cm. face area dry filler in 1 gr. of 1 gr. of Filler Weight mix of filler • filler McNamee Clay 9 .75 10. 76 215.2 6.18 Yorkshire Whiting 29-1 32 . 18 3 , 218. 0 92.34 60 mesh Silica 51 . 68 57 . 06 51 . 7 1.48 Total 90. 57 100. 00 3,484.9 100. 00.

The above figures illustrate the importance of the ■'percentage of the surface area a given filler occupies in the total surface area of all the fillers used in a particular formulation. The coarse filler ( 60 mesh silica) is 57 . 06 by , weight of the total weight of the filler mixture, whereas it yields 1.48$ of the total surface area of the fillers.

The latex used in Example 1 was Unitex, centrifuged natural Hevea latex of Stein-Kail. The dispersions of zinc ox-'' ide and sulfur are from R. T. Vanderbilt Co., marketed for latex compounding. Darvan 7 and Setsit 51 a**e also supplied by Vanderbilt as used. The water content of this composition is about 14. 66$, of which 9.8 $ is in Part A and 4.82$ in Part B, ' both based on total weight of the entire composition. Based on latex solids the approximate percentage of sulfur is 1$, of zinc oxide abdut 2$, and of the accelerator Setsit 1 , about 1 -1/2$. The anti-oxidant is about 1$ of the rubber solids.

The viscosity of the latex composition and its flow . characteristics are of importance for the proper application by slush casting. If the composition has too low a viscosity, thickeners are added. A sodium polyacrylate type thickener, like Polyco 2896 of the Borden Chemical Co., is suitable and is · used in water solution. If the viscosity of the composition is too high, it is thinned with water. The viscosity can be standardized by dipping standard panels into the composition and establishing the pick-up obtained by one dip. · Example 2 The following illustrates another useful latex com- ' position, i.e. j for forming rigidifiers.

In the composition of this example the latex used was Hycar 2β00 x 113, having 51. $ N.V. content. It is a reactive acrylic latex, having carboxylic modification in the polymer. Its film cures upon heating and its cure can be catalyzed by oxalic acid or ammonium chloride. Its film is soft and flexible and can be used as plasticizer for other latices. In this example the latex was used as the sole constituent of Part B, yielding 8.8 ^ elastomer, based on the total dry content of the composition. The fillers were the same having the same proportions and incorporated as described in Example 1. Darvan 7 was the dispersing agent in Part A. No other additives were present, except the fillers. Correction was made through slight modification of the water content. The ingredients mixed with ease and the composition could be applied with ease. Room tern- · perature drying was applied. Heating the dry inner layer for 3-7 minutes to 250-300° F. further improved toughness.

The water content of the composition was about 1β.3%-The rigidifier formed by this composition was excellent in .every respect. As shown, no crosslinking agent was applied, but such ,.c'ould be utilized.

Example 3 The following Illustrates a blend of latices and binder solids varied in relationship to the fillers, i.e., intermixes of high styrene SBR latex with Hevea latex.

In this example three preparations were made. a One of the latices used in the intermixes was a High Styrene SBR Latex, Polyco 2422 of the Borden Company. It has a 90 : 10 styrene to butadiene ratio and had about 50 N.V. content. The second latex in the intermix was the same Hevea latex used in Example 1 . In alternative 3-a the latex solids vjere in proportion of 20$ High Styrene SBR latex and 80$ natural rubber (Hevea) latex. Total elastomer solids were kept as in Example 1 . In alternative 3-b the relationship of the latices was 50$ ' to 0$ on dry basis and the dry content of the latex solids was roughly doubled based on the filler content. In alternative 3-c the latex mixture was in the proportion of 2 parts of natural rubber solids to 1 part of High Styrene SBR latex solids and the latex solids per filler content were tripled. The resulting compositions have been slush cast into similar' premolded shells and compared with each other after air drying and low temperature curing. The rigidifier of Example 3-a was more brittle than the one of Example 1 . It was still useful. The rigidifier of Example 3-b was stronger and less brittle than the one of Example 1 . The rigidifier of Example 3-c was stronger than that of Examples 1 , 3-a or 3-b.

The total filler content, based on total elastomer ,solids ranges from about 3-1/2-times in Example 3-c to about -1/2 -times in Example 1 . For formulation purposes the fine fillers (fines), which are pigment size particles, are in a .different category from the coarses. The fines cause increase in viscosity of the liquid composition as the loading is increased. The addition of the coarses hardly changes the viscosity of the liquid. The fines pass through a 200 or 300 mesh screen and may'' be even finer. The coarses pass through a coarse mesh screen, illustrated by a βθ mesh screen. The role of the coarses in forming this latex type of rigidifier is to promote drying speed, reduce the danger of mud -cracking and to lower the cost of the rigidifier component. Their presence improves the possibility of producing comparatively thicker layers per slush cast- ing step.

In an illustration of the useful pickup as an indication of the proper viscosity for slush casting, a premolded shell of 1 square foot surface area was coated by dipping and picked up 0.5 pounds in the first coat and 1 pound each in the second and third coats. After application of the three coats of rigidifier, the shell weighed 3.8 pounds, whereas the weight of the shell prior to the application of rigidifier was 1.3 pounds. The pickup weights are for wet pickup. The shape of the shell and the formulation of the latex composition may alter these figures. (2) Rigid Cellular Plastics as Rigidifiers.

Rigid cellular plastics are rigid plastics foams and' include both open cell and closed cell structures. They are well known in the art and are discussed, e.g., by T. H.

Perrigno in "Rigid Plastics Foams", Reinhold Publishing Corp., 1963 - The rigid plastics foams are Illustrated by rigid polyurethane foams, polystyrene foams, epoxy foams, polyvinyl chloride foams, syntactic foams, cellulose acetate foams, acyrlic foams, asphalt foams, amongst others. These rigid plastics foams are not equally suitable for the instant invention. The more useful ones will be discussed at greater length. The favored foam systems are illustrated by rigid polyurethane " foams .

In the preparation of polyurethane foams, several com-ponents. are used. Some of them permit the use of alternatives, others may be elective. One of the necessary components is a compound containing free isocyanate (-NCO) radicals. This com^- V ponent can be a polylsocyanate, usually a' diisocyanate, or a re^ action product thereof containing free -NCO radicals. Such reaction product may be an adduct, a prepolymer, a partial pre- polymer or a quasi-prepolymer, and is usually formed with a polyol. The second necessary component supplies active hydrogen atoms. These are usually supplied by free hydroxyl groups derived from a polyol or from a hydroxyl -terminated polyester. The free hydroxyl groups are reactive. As an alternative, polyesters or compounds containing reactive amine or carboxyl groups can also supply the active hydrogen atoms and be the second component. When free hydroxyl groups or free carboxyl. groups are reacted with free isocyanate radicals COg gas Is formed in situ in the reaction which in turn acts as the' foam forming gas. These types of foam are also known as carbon dioxide blown foams. Small quantities of water may be added. In many formulations catalysts are also present and optionally auxiliary foamers or blowing agents may be added, like tri- chlorofluoromethane. Surface active agents may also be present.

Aryl diisocyanates are preferred, but alkyl diisocya- nates may also be used. 2,4 tolylene diisocyanate and 2,6 tolylene diisocyanate are frequently used in admixture with each other and commercially available grades Include mixtures of these isomers in proportions of 6θ^-4θ^, 65%-35f a"d 80^-20^. Other examples are p, p' -diphenylme hane diisocyanate and. 'poly- methylene polylsocyanate (essentially a tri-functlonal isocyan- , ate marketed under the tradename o PAPI). Other suitable poly- lsocyanates are well known in the art. The principal commercially available polyhydroxy compounds are ethylene oxide and propylene oxide adducts of poly urictional active hydrogen compounds, such as glycerine, sorbitol, tr'imethylolpropane, ethylene diamine, sucrose, etc. These compounds are polyethers, but since they are primarily polyols, the term polyether polyol is properly used. Rigid foams require the use of highly functional reactants. These are most useful when based on polyalcohols having functionalities of at least 3 and in many cases greater than 3. The fluidity of the reactants at ambient temperatures is important as most of the time the reaction is carried out at room temperature and in the absence of diluents. Various hy- droxyl, carboxyl and amid bearing compounds may be reacted with polyisocyanates t.o form rigid foams. High viscosity saturated polyester resins illustrate some useful embodiments. The reactio product'of 2-1/2 mols of adipic acid, 1/2 mo1 phthalic anhydride and 4 mols of trimethylolpropane, having an acid num- ber of 35 and containing some residual water, illustrates a commercially available product.

The one-shot method of preparing polyurethane foams uses the original reactants. However, as the handling of idiisocyanates requires special and skilled care and precautionary measures, it became useful to pre-react the diisocyanates prior to foaming. The reaction is completed in a subsequent step. In this "prepolymer" method both the polylsocyanate and the active hydrogen supplying component are prereacted to an intermediate stage of the polymerization and the reaction is completed in a second step. The first step is carried out in the absence of moisture and the free -NCO content of the prepolymer is usually about 5 . Water is added prior to the second step foaming reaction together with the catalyst-emulsifier mixture. The prepolymer method is primarily adaptable to the preparation ' of high density foams, like those having higher pcf-values, like β pcf or higher. (Pcf = pounds per cubic feet). Prepolymers are very viscous and present problems in pumping and require small proportions of catalyst-emulsifier mixture, such as a ratio of 2 to 100 parts of prepolymer. This makes the metering difficult.

The quasi-prepolymers or partial prepolymers illustrate the favored materials for preparing rigidifiers. They are particularly advantageous with thermoplastic shells. The quasi- prepolymers are usually prepared by reacting about 4 to 4-1/2 equivalent weights of dlisocyanate with 1 equivalent weight of polyether polyol. The viscosity of. the quasi-prepolymers ranges between 4000' and 7500 cps. A given grade is standardized within 1000 cps +. With excess dlisocyanate, viscosities can be lowered to 100 cps or even less. The quasi-prepolymer is reacted with the proper quantity of additional polyether polyol just prior to the foaming operation. Surface active agents, catalysts and additional blowing agents may be incorporated with the additional polyether polyol and premixed therewith. Some of the advantages of the quasi-prepolymer method are: good storage ' '"■ stability of the reactant intermediates, suitable viscosity for pumping and metering, reduction of the noxious property of dlisocyanates, reduction of the exothermic reaction and the ability to produce uniform foams with primitive mixing equip- ment .

Catalysts are illustrated by nitrogen-containing compounds and by metallic compounds, such as dialkylethanolamines, \ N-alkylmorpholines, triethylenediamine, triethylamine, di-n- butyltln dilaurate, stannous octoate, amongst others. The preferred (surface active agents are organo-silicone fluids. They are organo-silicone block polymers. Copolymers of dimethyl polysilpxane and polyalkylene ethers are illustrative. One of the actions of these silicones is to keep the bubbles from breaking and thereby -prevent the collapse of the foam.

Halocarbons may be used as additional blowing agents. Trl-chloro luoromethane is an advantageous halocarbon, as its boiling point and evaporation characteristics are the most suitable for working close to room temperature. Flame retardant additives may also be mentioned as auxiliary agents.

For various specific effects other additives may also*' be present, such as cellulose derivatives to control bubble formation, and comminuted minerals to assist in reducing shrinkage after foam formation. Hydrous aluminum silicates and kaolinite illustrate., the latter group.

EPON 828 illustrates a commercial product, discussed further above., useful in the preparation of rigid . foams from liquid compositions. It has a viscosity of 50 to 150 poises at 5eC. and an epoxide equivalent of 175 to 210. The difunc-tional curing agents yield mostly linear polymers with -the di-functional epoxy resins. However, tertiary amines promote crosslinking between polyfunctional amines and epoxy resins. "\ The resin has to be preheated to. about 110°C. and this imposes limitations on its- use in this invention. Halocarbon blowing agents may be used in lo density foams. Silicone surface active agents assist in simplifying and extending the use of epoxy foams. Trichlorofluoromethane yields 2 pcf foams with ease.

Foam-in-place systems are available from various suppliers.

They are supplied as resin component and curing agent component, The resin component must be kept at 65°F. prior to mixing to prevent loss of halocarbon blowing agent. For commercial products the initiation time for start of foam rising is 30 seconds and foaming is complete in 1 to 3 minutes. The foam can- ' be handled in 15 minutes but keeping it in a mold for about 2 hours is recommended. Spray foam- compositions-, are also available'. The epoxy foams have excellent adhesion properties to various surfaces with which they are in contact while still liquid.

In selecting the rigid plastics foams, one has to consider the problems relating to the preparation of the articles of manufacture of this invention. The shell is formed in a mold. During the foam producing operation in some cases, the shell may be left in the mold in which it was prepared. In the majority of the cases, the shell is removed from the mold prior to the foam producing operation, and the foam formation is carried out either in a second mold or without the aid of any mold, using the shell itself for shaping the inner rigidifier foam. The foam after its formation is rigid and rigidifies' the shell... Therefore, where a second mold is needed, a multi-piece mold is required for ease of removal of the rigid manufactured product. (Especially where there are undercuts.) Such molds are difficult to operate and require precision tooling. Therefore it is of great advantage if. the rigidifier can be prepared in the absence of any molds, using the shell alone to shape the rigidifier. during its formation. Further problems arise when the preparation of the rigid foam requires temperatures at which the shell deforms; or if the foam shows excessive shrinkage after the foam-ing has been completed; or if excessive pressures are developed during the rise period of the foam.

■Quasi-prepolymer and prepolymer compositions are pre- poiyurethane ferred in the formation of/rigidifier foams, as they can be easily formulated with low shrinkage properties. However, more recently, one-shot type rigid polyurethane formulations have, also been prepared with low shrinkage properties. Efficient but slow mixing of the foamin components reduces shrinkage. According to a favored embodiment of this invention, the rigidifier is prepared in several layers of foam, thereby reducing both the problems arising from excessive shrinkage and from the formation of excessive pressures, and also permitting the formation of the rigidifier by the foam-in-place method but without the use of a second mold, i.e., utilizing the shell alone. for shaping the rigidifier. Compositions\ suitable for this type of method are also available today from epoxy resin rigid foams. Both of these compositions are also, suitable for spray application · if .properly compounded. Preheating of4the epoxy compositions to 100 to 110° C. is required Polyvinyl chloride type rigid foams can- be prepared by various methods. The gas releasing agent process can be carried out at fc§fflp§i?afcufas ar-eund 100e0. and melds ean be heated by steam of 100 PSI pressure. The required gelling and fusing temperatures require proper selection of shells and the presence of a second mold during the foaming process. Phenolic resin rigid foams can be prepared at room temperature and an after-cure at l o · to 200°P. is advantageous and sometimes required. They are brittle by nature and may require plasticlzation. The same applies to urea-formaldehyde rigid foams as to phenolic resin rigid foams. Polystyrene could be used with the expandable beads process. However, the heat required is in t e nature of 175 to 200°P. Foamed polystyrene is difficult to apply with use of the shell alone, i.e., without the use of a second mold. Silicone foams require higher temperatures, e.g., 300°F. Low requires elevated temperatures for manufacturing.

The most preferred rigid plastics foam formers for the purposes of this invention are the rigid polyurethane foam. ■r compositions. The next preferred foam formers are the rigid epoxy resin foam compositions. Thermosetting foams are preferred over thermoplastic foams. Low curing temperatures and fast foam setting rates are of advantage. sThe setting rate should not be so fast as to prevent the adequate distribution of the foaming composition throughout the inner surface of the shell.

Illustrations of quasi-prepolymer two-package systems are the Nopc'ofoam H-102N and bpcofoam H-103N systems, supplied by Nopco Chemical Company. They.' are marketed as two components: T-component and R-component. The T-component is the quasi-prepolymer formed by the diisocyanate and a polyether polyol. It has reactive -NCO groups and supplies the isocyan-ate radicals for the foaming reaction. It may also contain surface active agents, such as the silicones. The R-component contains the polyether polyols supplying additional OH-group-ings for the foaming and polyurethane forming reaction.' '·. In this H-series the R-component contains the fluorocarbon blowing agent, the catalyst, such as N-ethyl morpholine and dibutyl-tin dilaurate and may also contain all or part of the .surface active agents, such as the silicones. Trichlorfluoromethane is a suitable blowing agent. Its boiling point is about 7 .7°F. Mixing proportions of the respective T-component and R-component are obtainable from the supplier, together with mixing method, foam rise time, setting time and physical constants of the foams produced. They form rigid foams of 1-1/2 to 3 pcf density. The shell may advantageously be preheated to 100 to 130°F. to Improve flow characteristics and to fill areas of small cross- section. The higher the temperature the more rapid the foaming action, and a second mold may be required. The foam cures at room temperature in about 24 hours.

The polyisocyanate PAPI is suitable for formulating .one-shot rigid urethane foams. PAPI foaming compositions show lower exothermic reactions and shrinkages .

Whereas in most cases the rigid foam snugly attaches itself to the premolded shell, in some cases it is advantageous to apply an adhesive layer between the shell and foam to overcome possible effects of excessive shrinkage. A great variety of adhesives can. be used. Suitable adhesives are discussed further below. The adhesive causes the shell either to shrink with the foam or, providing the shell is strong enough, the adhesive causes the foam to adhere to the surface of the shell and prevents the former from shrinking away from the surface.

According to this invention^ one of the favored methods to avoid distortion by excessive pressure is the ' application ' of comparatively thin coats of foam in succession to obtain the required thickness of the rigidifier component. Another . effect can be obtained by placing a core in the interior of the shell cavity and foaming-in-place the rigidifier between the core and the interior surface of the shell. The core may be a plastics skin, or paper chipboard, or the like.. Designing the shape of-the shell to provide a comparatively wide access opening to- its cavity will also assist in reducing the formation of excessive pressures. Filling of the cavity by successive incremental horizontal layers of foam can also be used.

The rigid foams may either fully fill the cavity of the shell or be formed within the shell to define a cavity. In this latter case, an ancillary reinforcing element may advantageously be present. Such elements will be discussed further ^below. Densities of 1-1/2 to 6 pcf are preferred. Higher density rigid foams may also be used, particularly in multilayer foam application. The first applied foam compositions may have in such cases as high a density as 20 to 25 pcf, followed by less dense foam layers. Application by slush casting or rotational casting is preferred. In some cases spray application is feasible.

As it will be seen, rigid polyurethane foams may also be used as ancillary reinforcing elements with other rigidifiers of this invention. (3 ) Rigid synthetic resin compositions,, comprising a rigid polyester resin or a rigid epoxy resin, as rigidifiers'..

Polyester resins and epoxy resins may be used in this invention at various positions. The flexible resins may form shells and .ancillary reinforcing elements. The rigid resins form a useful range of rigidi iers. The chemistry of these resins is well known in the art. Therefore only brief data are given here to assist in the proper selection of the resin for the rigidi- fier.

•The aromatic dibasic acid in the polyester formulation adds compatibility, controlled reactivity, hardness and strength. Isophthalic acid may be used. As flexibility and/or resiliency may be enhanced by incorporation in the acid component of some adipic acid, sebacic acid, azelaic acid, di er vegetable oil acids, and others, their absence assists in obtaining rigid polyesters. As mentioned, flexible polyesters usually contain long chain acids,- or glycols, or both.- Propylene glycol yields rigid resins. Diethylene glycol, triethylene glycol and other monomer content ranges from 25$ to 50$ by weight. 40$ styrene content illustrates a useful proportion. Specialty monomer, effects can be obtained, for example, with diallyl phthalate, diallyl isophthalate, triallylcyanurate and methyl methacrylate monomers. LAMINAC Polyester Resins 4128 and 4123 illustrate two rigid polyesters. LAMINAC Polyester Resin EPX-126 -3 is 'a flexible polyester resin containing styrene monomer. Polyesters are classified as "rigid" or "flexible" according to the degree of stiffness in bending. This is measured by the flex-ural modulus which is the modulus of elasticity in flexure, expressed in PSI values. The Modern Plastics Encyclopedia, 1966 edition on page 291 gives a table of classification. (Published in September, 1965 , Vol. 3 , No. 1A. ) The rigid polyesters have a modulus of elasticity in flexure of at least 3 x 10^ PSI. Most rigid polyesters have tensile elongations at break of 1 to 2$ whereas flexible unsaturated polyesters have elongations as high as 200 or more. Example 4 illustrates a satis actory polyester compositsion for t e rigidifier component , Example 4 The following illustrates a useful rigid polyester for formation of the rigidifier.

A rigid polyester slush casting composition is prepared by mixing.41.3 $ of LAMINAC Polyester Resin 4128, 0. cobalt naphthenate ( 6$ Co), 41. 34$ of 325 mesh silica ( flint'), 16. 53$ of 60 mesh silica (flint), and 0. 69$ MEK peroxide, totaling 100$. The ingredients are mixed in the order of listing. The setting time of this filled polyester composition can be varied by changing the proportions of the catalyst (MEK peroxide ) and cobalt metal content. The polyester resin used in this example gels at room temperature , in absence of fillers, in time intervals ranging from about 10 minutes with io catalyst . and 0.3$ cobalt naphthenate (6$ metal content) , to about l80 minutes with 0.5$ catalyst and absence of cobalt naphthenate. In these gelling tests, the MEK perPxide is applied as catalyst in a βθ solution. The setting time at room temperature of the filled composition of this example may be varied from about 4 minutes to about several hours.

Epoxy resins are characterized by the presence of epoxy groupings. Reference is made to Modern Plastics Encyclopedia, 19ββ edition., pages 165 to 169 · If we consider the \ number of the linkages in the condensation reaction of bisphenol A with epichlorhydrin converted to ether linkages as "n", one can visualize that "n" could be zero .or more. The resins containin "n" equal to 0 to 1 are liquid and are preferred for the purposes of this invention. They polymerize to rigid resins and may be plasticized with epoxy plasticizer resins, like the low viscosity, liquid aliphatic polyepoxides . EPON Resins 828, 830 and 83 are rigid resins marketed by Shell Chemical Corporation and EPON Resin 871 illustrates a liquid aliphatic polyepoxide, which comprises unsubstituted 2,3-epoxyalkyl esters of mixtures of dimer and trimer fatty acids having 12 to 30 carbon atoms.

The selection of a curing agent or hardener for epoxy resins depends on the application method.' Suitable curing agents include diethylenetriamine, N-amino-ethylpiperazine, triethylene-tetramine, NADIC methyl anhydride, adipic anhydride, dodecenyl-succinic anhydride. Catalysts include borontrifluoride-mono-ethylamine, dicyandiamide and benzyldimethylamine . Flexibility and rigidity may be regulated, for instance, by the percentual. proportion of the bisphenol A comprising rigid epoxy resins an.d of the liquid aliphatic polyepoxides . Other epoxy resin plas-ticizers are epoxy compounds of fatty oils and their acids.

Polyamids may also be used, as curing agents.

Example 5 The following illustrates a suitable epoxy resin composition for formation of the rigidi-fier.

This composition has the following weight part's: EPON Resin' 828 100 parts, Epoxide #7 (Procter & Gamble) 5 parts 325 mesh silica 100 parts, βθ mesh silica' 100 ' parts, diethylene triamine 10 parts, totaling 315 parts. A small quantity of Cab-O-Sil can be added to regulate viscosity and drainage time. This additive increases viscosity and decreases drainage' time on vertical surfaces. The composition of this example is suitable for fiberglass reinforced applications. ^ A limit of 10 elongation at break is a reasonable \ top limit to characterize rigid epoxy resins . The flexible epoxy resins have elongations at break exceeding 10%. or rigid epoxy resins may advantageously be reinforced by fi- '· brous materials, such as fiberglass. In most cases this requires large access openings in the shell to accommodate the necessary tools, and therefore it is practical for larger objects only. Fiberglass reinforcements are supplied as continuous strands, fabrics, mats, chopped strands, and other forms. Other useful fibrous reinforcements may include sisal, cotton, · jute, asbestos, synthetic fibers, metallic fibers, and the like Methods of fiberglass reinforcement are well, known in the art. Pilled (filler containing) polyester and epoxy resin compositions are preferred, as the fillers reduce shrinkage dur ing curing and have other advantages. Silica illustrates a suitable filler and 325 and oO mesh grades are illustrative of suitable grades.

* Some of the rigid polyester resins and epoxy resins have limited adhesion properties to some of the shell components and the application of an adhesive between the shell and the . rigidifier is required. The rigid polyesters and rigid epoxy resin rigidifiers are somevhat brittle., and their toughness is improved by fibrous rein orcement , even though they are well protected on one side by the pliable shell. However, in most cases, particularly where fibrous reinforcement is absent, it is advantageous to provide for an ancillary reinforcing element, such as an adhering layer of flexible epoxy resin composition, or of a flexible polyester composition.

The favored application of the types of rigidifier ac¬ cording to this invention is from a liquid state. Various suit^ July 8f able methods are available. Casting is a suitable method, such as slush casting, or rotational casting, or centrifugal casting Other methods Include brush application and spraying. The viscosity of the liquid composition is adjusted to supply the re- 20 squired flow and drainage properties desirable for the particular application method selected.

July 18, In many instances it is advantageous to apply an ad¬ " 966 hesive as an intermediate layer bet een the shell and the . igidifier,j for example, when the shell is derived from plasti7 sol and the rigidifier comprises a rigid polyester resin. Rigid polyurethane foams as rigidifiers may also be improved in many instances by the application of an adhesive layer.

Neoprene cement illustrates a suitable adhesive type.' Columbia Cement Company's Neoprene Cement Mo. 7^2 illustrates this group. It can be applied from a dilute solution, using % of the cement composition and 80$ methylethyl ketone (ME ), proportions being by weight. This solution can be applied' by slush casting to the interior surface of the premolded plastisol shell through its access opening and air drying the deposit.

Other suitable adhesives include resorcinol adhesives, asphalt adhesives, rubber emulsions , rubber solutions (rubber cements), epoxy resin adhesives, special polyester resins, latex adhesives, latex modified cements, and the like. Still other suitable adhesives include: (1 ) Solutions of VINYLITE Resin VAGH in solvents, as in methylethyl ketone, or in mixtures of toluene and methylethyl ketone. This is a copolymer of vinyl acetate, vinyl chloride and vinyl alcohol, and is compatible with alkyd resins and polyesters. (2 ) Polyurethane adhesives of the 2 part and 1 part systems. (3) An adhesive containing vinyl resins, methylethyl ketone, dioctyl phthalate and methylene-bis ( -phenyl isocyanate). (4) Nitrile rubber adhesives. (5) Nitrile-phenolic adhesives as discussed on page 0 , col. 2 , par. 6 of Handbook of Adhesives, by Irving Skeist, Reinhold. Publishing Corp., 1962/64. See also pages 236 to 24l of same publication. \^ According to one embodiment of this invention}- im-proved adhesion is achieved by the use of a joint "contact resin" ingredient, present both in the shell and the rigidifier.- Ancillary reinforcing elements can be applied behind the rigidifier in cases where the shell and the rigidifier jointly form a cavity. This is particularly advantageous when the composite article of manufacture is. exposed to high' j stresses and/or pressure. Such an ancillary reinforcing element assists-, he: rigidifying action of the rigidifier, I toughens the composite article and increases its resistance ! j to impact. The element may he continuous or discontinuous..

J The ancillary reinforcing; element may he of metal, paper j I chipboard, cardboard, or other suitable materials0 When it is continuous, and it is formed from a liquid, it maybe applied by casting, such as slush casting or rotational 1966 casting. Materials applicable by casting are low melting- point metal alloys, rigid cellular plastics compositions (like polyurethane foam compositions) which may be foamed- in-place type compositions, and others. The rigid plastics · foams are illustrative of useful materials for the ancillary reinforcing element when it is- to fill completely the ■ cavity formed jointly by the shell and rigidifier.

The ancillary reinforcing element may also be of a. synthetic resin layer. Materials: applicable by casting may also "be flexible epoxy resin* composi ion., or flexible, polyester compositions.

The favored ancillary reinforcing elements for the rigid synthetic resin type rigidifiers are the flexible epoxy resins and flexible polyester resins.

Example 6 Thi3 illustrates, a suitable, epoxy resin composition for the formation of ancillary reinforcing elements- A flexible epoxy resin composition is- prepared of the following ingredients: 15.0 ΕΡ0ΪΤ Resin 871 , 1'5oO¾S EP017 Resin 828, 6.1¾£ Epoxide #7 (an epoxy plasticiser of Procter & Gamble), 30 o 20# of 325 mesh grade silica, 3C.2Q3 of 60 mesh grade, silica, 3 o 0Cj£ of diethylenetriamine (DTA) and . > of Cab-0-Sil, totaling 1 0Q£O The nature of some of the ingredient's are des When "the composite article of manufacture of this invention is a tile with a textured surface, the ancillary reinforcing element may be a prefabricated board, such as paper chipboard, cardboard, cement board, plaster board, Masonite board, or other suitable material. A fiberglass reinforced rigid polyester composition may also be used as a reinforcing element.

In order that the disclosure will be more fully understood and readily carried into effect, the following detailed description is given with reference to the accompanying drawings : FIGURE 1 is a vertical cross-sectional view of a •single piece mold utilized in this invention. 19 is the metal mold. It shows an undercut 19a ; .

FIGURE 2 is a vertical cross-sectional view of the mold 12 of FIGURE 1 in which a shell 20 was molded. As described ea lier, plastisols illustrate suitable shell orm ng materials. The plastisol composition may be applied by slush casting, the deposit heated to gelation temperatures, followed ■by heating to fuse the gelled shell.

FIGURE 3 is a vertical cross-sectional view of the mold 1 of FIGURE 1, illustrating the removal from the mold of the shell 20, advantageously formed by plastisol. Such plastisol shell is in a somewhat collapsed state, but re- , · , gains its original shape after removal and cooling.

FIGURE 4 is a vertical cross-sectional view of a composite article of this invention. The shell 20_ was molded in the mold of FIGURE 1 and a rigidifier 21 is snugly attached to the inner surface of said shell. The shell and rigidifier jointly form a cavity 42 . T *-sii^a½-e-^_^^^"^^ A suitable rlgidlfler is; illustrated/ fby a rigid composition comprising a filler bonded by the elastomer solids of a latex, discussed in greater detail further \ bove. The rlgidlfler 2l_ is shown as a single layer, but may . bQ several layers.

FIGURE 5 illustrates a vertical cross-sectional view of a composite article of this invention. 20 is the molded shell. 22-a, 22 -b and 22-c illustrate three individual layers of rlgidlfler, which may be rigid polyurethane foam. To secure even distribution, they are poured-in-place in successive increments through the. access opening 3 of the shell, and each increment coats the surface of the cavity 4 _ while the shell is being rotated and the foam forming composition is still liquid. 22-a, 22-b and 22-c jointly form the rigldifier. The embodiment of FIGURE 5 reduces the quantity of polyurethane foam utilized, reduces shrinkage and, by reducing the pressure during foam expansion, eliminates the need for an outside mold during the foaming Operation. In one embodiment of the invention, the composition of the three rigidifier layers may vary, 22-a having a density, for instance, of 20 to 25 pcf and 22 -b and 22-c having a density of about 2 to 3 pcf. In another embodiment all three layers are of a foam with a density of from about 1-1/2 to about 3 pcf, FIGURE 6 illustrates the vertical cross-sectional view of an article wherein the cavity formed by the shell 20 is .fully, filled by the rigid polyurethane foam rigidifier composition 22_. In preparing this product, a second mold, i.e., a temporary supporting mold, may be necessary. Such a temporary supporting mold may be provided by a multi-piece mold as previously described, or advantageously, a temporary one-piece mold may be formed to provide the necessary support against the internal For example,■ a plaster of paris mold may be applied to the shel], e.g., by dipping or spraying, etc., prior to foaming. Other materials, such as low melting point metals, may be used instead of the plaster of paris. The temporary supporting mold mixture is allowed to solidify prior to the foaming-in-place step.

After the foaming is completed, the temporary supporting mold is removed, e.g., by cracking, peeling, melting, etc. By careful control of exothermic heat, pressure developed on expansion of foam, etc., it is possible to produce the same article with no temporary supporting mold whatsoever.

FIGURE is a vertical cross -sectional view of a lamp. is the shell. 21_ is the rigidlfler, advantageously a rigid composition comprising a filler bonded by the elastomer solids of a latex. 23_ is an ancillary reinforcing element, made of · rigid RDlyurethane foam, partially filling the cavity jointly formed by the shell and the rigidifier. 24 is a metal tubing. i a jgta.2 i§m. base, 2j is a jarn ς>ςΚ§£ fgr- ei§ctrical bulbs. The metal tubing 24 carries the electrical wiring to the socket. The ancillary reinforcing elment 23 is applied here ito a part of the surface of the cavity jointly formed by the shell and rigidifier.

FIGURE 8 is a vertical cross-section of a refrigerator door, shown in front elevation in FIGURE 8A. 20 is the shell. 21 is the rigidifier, which is advantageously a fiberglass reinforced rigid polyester resin. 37. indicates. an adhesive layer. 23. is a rigid polyurethane foam, applied as an ancil- lary reinforcing element fully filling he cavity jointly formed by the shell and rigidifier. 40 illustrates textured decora- ■ tive effects formed in a portion of the shell which provides the surface of the front side of the door. The decorative effects are achieved in the process of molding the shell. The texture gives a discontinuous decorative pattern.

FIGURE 9 is a vertical cross-sectional view of a hollow article. SO is the shell. 81 is the rigidifier which suitably is a latex bonded composition. 27 is an ancillary reinforcing element made of metal utilized to strengthen the narrow neck portion of the manufactured article. This illustrates the use of an ancillary reinforcing element applied to a portion of the inner surface of the rigidifier.

FIGURE 10 illustrates the use of an ancillary reinforcing element applied to the entire interior surface of the rigidifier. The shell is 20. The rigidifier is 21, and 28 is the ancillary reinforcing element, advantageously a resinous composition comprising a flexible epoxy resin or a flexible polyester resin. The rigidifier 21 in this figure may be of a composition comprising a rigid polyester resin.

FIGURE 11 is. a vertical cross-sectional view of an arm rest part of a piece of furniture. 20 is the* shell. 2_1 is the rigidifier, which may be made of a late bonded composition. 2j+ is a metal tube acting as an ancillary reinforcing element and l is a layer of filled^ polyester, with a filler i such as silica, acting in a similar manner to the rigid poly-urethane foam in FIGURE 8.

FIGURE 12 is a vertical cross-sectional view of. a composite article. 20 is the molded shell. 29 is a tube placed into the internal cavity of the molded shell. The tube can be made, e.g., of chipboard paper, or of aluminum metal, or the like. 22 is a rigidifier which may be of the rigid poly-, urethane foam type. The foam is formed around the tubing. The tube reduces the inward shrinkage of the foam and also reduces the quantity of the foam required.

FIGURE 13 is a cross-sectional view of a three-dimensional illustration of a composite article of this invention. The Illustrated article has vertical and. horizontal cross- sections which are both rectangular.' The flat surfaces of this type of object have a greater tendency to be pushed outward during foaming in a single stage foam filling operation, as a consequence of the foam rise. A "layer method" of foam filling eliminates the excessive pressure during foaming and simultaneously may eliminate the need for an outer, protective mold during the foaming. 20 is the shell. 3 , 34-a, 3^-b, 35, 3- \ -b, 36, 36-a and 36-b illustrate 9 individual layers of rigid polyurethane foam prepared in successive foaming steps.

FIGURE 14 and FIGURE 15 are vertical cross-sectional views of related and alternative composite articles of this invention. 201s a shell. 22 is a thin layer of molded plastics skin protruding into the internal cavit of the molded shell . During the foaming operation, this thin layer of skin 30_ can be supported by a plug 31 which is then withdrawn after the •foaming operation is completed. 22 is a rigid polyurethane foam which has bee prepared by foaming around the plastics coated plug. The foam fills out the space between the plastics coated plug and the shell. FIGURE 14 illustrates : the embodiment wherein the plug 2i haa Deen removed after the foaming is completed, leaving the thin layer of plastics skin 30 as a coating on the interior of the foam layer 22. This alternative is useful for thermally insulated containers. In the alternative illustrated by 'FIGURE 15, both the skin 30 and the plug 31 have been withdrawn and the space obtained by such withdrawal is filled with a second quantity of rigid polyurethane foam 32. In this , alternative, 22 supports the shell and retains the inner foam layer 2 during the second foaming operation. In FIGURE 15, the ^density of the foam of 22 may be from about β to 25 pcf and that of 22 may be from about 1-1/2 to about 3 pcf. The high density foam performs the main task of rigidification and prevents distortion during the second foaming step without the use of a protective mold during foaming. In some cases the use of a two piece mold or multi-piece mold during the foaming operation may be advantageous.

FIGURE l6. is a modification of FIGURE 10 and it shows the simultaneous.. use. of an adhesive layer 37 and an ancillary\ reinforcing element 2J3. 20, 2_1 and 28 are described more fully^ in FIGURE 10. The adhesive layer 37 is between the shell and the rigidifier.

FIGURE 17 is a cross-sectional view of a tile made according to this invention. This type of tile has a textured surface on its facing. The texture is molded into the shell which provides the facing of the tile. 21 is the rigidifier formed from a fluid state. 0 is the sculptured raised tex-ture of the shell 20. 3 is an adhesive layer and 38 is a reinforcing board applied as an ancillary reinforcing element. Various board materials are listed further above which are useful as ancillary reinforcing elements. In' this illustration, the board is the backing of the tile.

FIGURE l8 is a cross-sectional view of another tile. is the shell having a textured surface on its face. The shell is first formed in a mold. The. rigidifier 21 is formed from a fluid state, e.g., by slush casting into- the shell. This is made possible by the shape of the shell which has low sidewalls. 28 is an ancillary reinforcing element formed by pouring a fluid resinous composition, like a flexible epoxy resin composition into the regidifier 21. The tile illustrated by FIGURE 18 has been cut and/or ground flat, after the ancillary reinforcing element has properly hardened, thus forming the illustrated tile which has a smooth back side.

FIGURES 17 and 18 illustrate' tiles having a textured surface on their facing. The expression "textured" includes raised and incised discontinuous patterns of decoration, such as embossed and carved designs, respectively. It also includes discontinuously curved surfaces. The shell of the tiles illustrates the alternative where the hollow shape of the shell is characteristic only to portions of its inner surface. The thickness of the tiles preferably range from about l/8th of an inch to about 2..inches . These limits correspond to a thickne&s ranging from about 125 to about 2000 mils. If the dimensions i length and width are comparatively larger, as for instance, when they are longer than a .foot, the tile could be called a. panel. Whereas the rigidifier primarily reinforces the textural portions of the shell component of the tiles, it reinforces also the shell component in its entirety.

Claims (1)

1. 26165/2 Clalma j July 18> 1966·"*' 1. A rigid composite article of manufacture comprising .an outer shell and an inner rigidifier, said shell being a pretnolded flexible and pliable plastics material, said shell having inner walls defining an internal cavity accessible through an opening in the shell, said rigidifier being a rigid material formed within said internal cavity in ' intimate supporting contact with the inner walls of said shell to maintain said shell in its premolded shape. \ July 18, 1966 2. The article according to Claim 1, in which the walls of said shell have a thickness of from about 15 1/2 mils to about 250 mils. July 18, 1 66 3. The article according to Claim 1 or 2, in which. parallel cross-sections of the article show varying measurements and shapes. July l8, 19βο 4. The article according to Claim 1, 2 or 3, in " - which a layer of adhesive is present between the shell and the' rigidifier. July 18, ·19ββ 5. The article according to Claim 1, 2, 3 or 4, in which the shell and the rigidifier Jointly form a . cavity. 261 68/2 July l8 , 19ββ β. " The article according to Claim 5, n which an ancillary reinforcing element is positioned within the cavity jointly formed by the shell and the rigidifier. July 18 , 1966 7 · The article according to any one of the preceding claims, in which the shell comprises a thermoplastic ·. . plastics. . \ July l8 , 1966 8. The article according to any one of the preceding claims, in which the shell comprises vinyl chloride in a polymerized and plasticized state. July 18 , 19ββ 9. The article according to any one of Claims 1 to 7, in which the shell comprises ethylene in a polymerized state. July 18 , 19ββ 10. The article according to any one of Claims 1 to 9, in which the rigidifier comprises plaster of paris in a set state. ' . July 18, 1966 11. The article according to any one of Claims 1 to 9, in which the rigidifier comprises asphalt. July 18, 1966 12. The article according to any one of Claims 1 to 11 , in which the shell and the rigidifier jointly form a j cavity and a rigid polyurethane foam is used as an ft ancillary reinforcing element positioned within the i · • cavity. 26168/2 i July 18, 1966 13. The process of producing rigid composite articles of manufacture comprising an outer shell and an inner rigidifier, which comprises the combination of the steps of molding a flexible and pliable plastics material in a die to form said shell having inner walls defining an internal cavity accessible through an opening in the shell, applying through the opening in the shell to the entire inner walls of said shell a liquid composition suitable to form said rigidifier, and causing the said liquid . composition to solidify in intimate supportin ^con- tact with the inner walls, of said shell. \ July 18, 1966 l . The process according to Claim 1 , in which the premolded shell is stripped from the die prior to the application of the liquid composition suitable to form the rigidifier. ; July 18, 1966 15. The process according to Claim 13 or 1 , in which' . the step of forming said shell includes casting a I " plastisol composition in a die, heating the plastisol to . gelation temperature and fusing the gelled plastisol ''■ layer to form a tough premolded shell. July 18, 19ββ ΐβ. The process according to Claim 15-, in which the heating and fusing steps are carried out in a manner ; to yield a shell with a wall thickness of at' least about 15 1/2 mils and not substantially more than about 25Ο mils. 2β> 68/2 17 · The process according to Claim 13 through l6 in which the die is a seamless die. 18. The process according to any one of Claims 13 through If, in 'which the liquid composition suitable to form the ' rigidifier is distributed evenly on the entire surface of the inner walls of the premolded shell. 19 · The process according to any one of Claims 13 to 18, in which an adhesive is applied to the surface of the inner walls of the premolded shell prior to the application of the liquid composition suitable to form the rigidifier. 20. The process' according to any one of Claims 13 to 19 , in which the steps are carried out in a manner such that the shell and the rigidifier jointly form a cavity, and an ancillary reinforcing element is applied to at least a portion of the interior surface of said cavity. 21. The process according to any one of Claims 13 to 20., in which a removable supporting mold is present during the formation' of the rigidifier to support the premolded shell. 261 o8/2 July Τδ, 22. T e; process, according to claim 21 ,- in which 1'966 the. removable supporting mold is formed "by applying plaster of pari3 to the outside of the premolded shell. 23· The article according to any o e; of claims 1 -9 , in which the rigidifier comprises a thermosetting plasties in a thermoset state. 21+· The article according to any one of claims 1 to 9, in which the rigidifier is: a rigid composition comprising a filler "bonded by the elastomer solids of a latex. 25. ' The article' according to any one of claims 1 to 9 » in which the rigidifier is a rigid cellular plastics composition. 26· The: article according to any one of claims 1 to 9 » in which the rigidifier is a rigid polyurethane foam composition. 27· The article according to any one. of claims 1 to 9, in which the rigidifier comprises a rigid polyester resin composition,, 28. The article according to any one of claims 1 to 9, in which the rigidifier comprises a. fiberglass reinforced polyester resin composition. 261.68/2 29. The; article accordin to any one: of claims 1 to 9» in which the rigidifier comprises a rigid epoxy resin composition. 30. The article according to any one of claims^ 1 to 9» n which the rigidifier comprises a fiberglass reinforced epoxy resin composition. 31 « The article according to a y one of the preceding claims, in whic the shell and the rigidifier Jointly form a cavity and a flexible epoxy resin is used as- an' ancillary reinforcing element over the entire inner surface, of the cavity. 32. The article according to cl ims 23-30 in which the shell and the rigidifier jointly form a cavity and a rigid polyurethane foam is used as an ancillary reinforcing element positioned within the cavity. 33· The; article; according to any one: of the preceding claims, in which the article is a tile having a textured surface, said texture forming the hollows of the- shell ait least on a portion of its surface-. 34* A. rigid composite article of manufacture substantially as hereinbefore described'with reference to and. as illustrated in the accompanying drawings. 35. The process of producing rigid composite articles substantially as hereinbefore described.