Calcium Carbonate as Filler

The addition of a mineral such as calcium carbonate to polyethylene was found to increase the toughness of the polyethylene and increase the softening point temperature. The ICI scientists obtained US. Patent 2,466,038 on April 5,1949, describing a composition that was produced by the addition of calcium carbonate (30 wt%) with a particle size of less than 0.1 micron and polyethylene (70 wt%). 

5 Examples of Additives Presently Used in the Polyethylene Industry (2012) 

Presently, there are a wide variety of compormds that may be added to polyethylene to improve the performance of polyethylene in end-use 

---

However, it has been found that a filler can be added within a specified range to provide a suitably tearable filled thermoformed HIPS container lid when the tear back portion of the lid is oriented in the extrusion direction of the PS, when the tear back lid comprises two sets of tear indentations and a tab portion. In this way, the lid is prepared from a HIPS composition consisting essentially of from 10-15% calcium carbonate as filler (28). 

Five were clay filled and one had lime mud (calcium carbonate) as filler. The fiber furnish varied from all rag to mixtures of rag and sulfite wood pulp, to all wood fibers.. . . The sixth sample which had the lime mud was 75% sulfite and 25% soda wood fibers it had a pH of 8.9, while the other five samples had pH values varying from 3.6 to 4.3. When Edwin Sutermeister examined the samples in 1929 and retested them, his report said, all of the acid samples were badly discolored and were absolutely without strength, while the lime mud sample was much whiter and seemed as strong as ever. ... 

Floor-covering adhesives are used for gluing down flexible floor coverings, such as carpet or vinyl sheet. In Europe predominantly acrylics are used, formulated with tack-ifying resins and calcium carbonate as filler. In North America usually high solids content styrene-butadiene emulsion polymers are applied, formulated with naphthenic oil and clay as filler (Urban Egan, 2002). In either formulation the inorganic filler content is between 25% and 50% and the polymer/resin ratio is about 1. 

Ceramic-tile adhesives are used for thin-bed applications on wall and floor, gluing tiles onto flat surfaces. Non-cementitious adhesives (mastics) are made of acrylic emulsion polymers (ca. 20%) mixed with silica sand and calcium carbonate as fillers (ca. 80%). One-component cementitious ceramic-tile adhesives are made of cement (ca. 35%), redispersible polymer powders (1-25%) and fillers, such as silica sand (Lutz Hahner, 2002). The redispersible polymer powders are made from emulsion polymers, which are spray dried. Predominantly vinyl acetate copolymers are used. 

At the same chlorine content, CPE evolves considerably less hydrogen chloride dining combustion tests. PVC/CPE combinations should be considered for apph-cations requiring low corrosive gas evolution. The most common compounding technique is to use ultrafine calcium carbonate as filler for maximum hydrogen chloride absorption. This may be necessary in replacing lead stabilizers (whose reaction products with hydrogen chloride are typically very heat-stable) with zinc-based equivalents. 

The gluability of the lignin-epoxy resin adhesives was found to be improved by the addition of calcium carbonate (50% by weight) to the liquid resin. This must be attributed to the nature of the weak alkali in calcium carbonate as a cure accelerator, and to the reinforcement effect of fillers. Since wood surfaces are acidic, the addition of alkaline fillers effectively alters the pH of the glue line. 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

Calcium carbonate cannot be used in the same low pH papermaking process that contains alum and rosin size. The presence of carbonate in an acid papermaking process causes severe problems such as foam, excess alum demand, inefficient sizing conditions with rosin size, and troublesome deposits. The alkaline system, therefore, enables the paper-maker to use calcium carbonate as a primary filler as well as to use more recycled paper. 

The observation that acid hydrolysis is avoided by fabrication of paper which is neutral or slightly alkaline has led to the incorporation of an alkaline filler such as calcium carbonate. Some very old papers which contained calcium carbonate as a loading material or as residues from processing of the fiber stock have shown excellent stability. 

Phyllite (containing quartz, muscovite andkaolinite) was compared with calcium carbonate as a filler for poly(vinyl... 

The concept of lower water vapor permeability has been tested in comparison to a silicone based RTV-2 system (Elastosil SG 500 from Wacker Silicones) according to DIN 53122-1 (samples were 2 mm thick). The Poly bd RT 45 HTLO-based sample also contained ground calcium carbonate as a filler. It can be clearly seen that the overall permeability is significantly lower for the novel RTV-2 system. 

Huggenberger L, Neubold H B. Pigments for Paper. Natural Ground Calcium Carbonate as Coating Pigment and Filler. 

While the presence of a filler affects the way a matrix crystallizes, the opposite is also true. In studies of in situ formation of calcium carbonate in different copolymers, different crystalline forms of calcium carbonate were found. Calcium carbonate crystallized without a polymer had a rhombohedral morphology. When crystallized in the presence of polyethylene oxide its morphology remained rhombohedral because the polymer does not interact with the crystal of calcium carbonate as it... 

Apparently, none of WPC manufacturers adds calcium carbonate as a filler in then-products. LDl Composites, which use Biodac that consists of about 25% CaC03 and 25% of kaolin (clay), also did not use individual minerals as fillers. Nevertheless, there are many publications, mainly by suppliers of minerals and university researchers, describing benefits of calcium carbonate in WPCs. 

Table 14.11 Effect of Calcium Carbonate as a Filler on the Oxygen Permeability of PE...

Biodentine is supplied as a powder and a liquid. The powder contains, in addition to the calcium silicates, calcium carbonate and calcium oxide as fillers, iron oxide for pigmentation, and zirconium oxide as a radiopacifier. The liquid is mainly water and contains calcium chloride as an accelerator, plus a water-soluble polymer [70]. 

Reinforcements are used to enhance the mechanical properties of a plastic or elastomer. Finely divided silica, carbon black, talc, mica, and calcium carbonate, as well as short fibers of a variety of materials, can be incorporated as particulate fillers. Incorporating large amounts of particulate filler during the making of plastics such as polypropylene and polyethylene can increase their stiffness. The effect is less dramatic when temperature is below the polymer s Tg. 

Polypropylene that is reinforced with mineral fillers, such as talc, mica, and calcium carbonate, as well as with glass and carbon fibers. The maximum concentration is about 5 wt%, although concentrates with higher levels of filler or reinforcement are available. 

Selected unsaturated carboxylic acids are particularly useful as coupling agents for calcium carbonate-type fillers. They interact strongly with the basic surface of the carbonate, unlike silanes that only show a weak interaction. In addition, unlike simple saturated carboxylic acids, which just have a beneficial effect on impact strength, unsaturated carboxylic acids may increase tensile strength. Table 6.5 illustrates this effect in a 60% filled CaCOs/PP homopolymer system. This system is heavily stabilized with both hindered phenol and phosphite-type antioxidants, and a small amount of peroxide was therefore added. 

An application of calcium carbonate as a bioactive filler was discussed by Kasuga et al. [19], who incorporated vaterite powders prepared by a carbonation process in methanol into a polylactic acid matrix. Composites containing 20-30 wt% vaterite... 

Zhou and co-workers [27] used calcium carbonate as a reinforcing agent for sulfonated PEEK. The calcium carbonate particles were surface treated and the effect of this on the mechanical and thermal properties were determined. The modulus and yield stress of the composites increased with CaCOs particles loadings. This increase was attributed to the bonding between the particles and the PEEK matrix. DSC experiments showed that the particle content and surface properties influenced the Tg and the T of the composites. The Tg increased with the content of fillers while Tn, decreased. The treated fillers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. 

Fillers and additives are specifically added to enhance the specific performance, reduce cost, change viscosity or improve processibility of resin systems (Owens Coming, 2003). Dry fillers usually make up the largest proportion (up to 50 wt%) of a resin formulation. Commonly used fillers in pul-trusion include calcium carbonate as a volume extender, alumina silicate or clay to build corrosion resistance and electrical insulation, and alumina trihydrate for better fiame or smoke retardation and electrical arc resistance. Additives are meant to tailor specific performance or properties. These typically include initiators to influence resin curing, mould release compounds such as metallic stearates or organic phosphate ester, antimony oxide for flame retardance, pigments for coloration and agents for surface smoothness and crack suppression. 

Carpet Recycling. By the beginning of the century, about 4.7 million tons of residential carpets were disposed of annually in the United States, with less than 5% being reused or recycled (56). Scrap carpet is bulky and difficult to collect. Efforts are underway in the United States to reduce landfilled carpets by 40% by 2012. Carpeting is a complex product consisting of 40-60 wt% of yarn from PA-6, PA-66, PET, and PP, 4-6% of primary backing made from woven PP, 38-52 wt% of adhesive made from styrene-butadiene latex with calcium carbonate as a filler. 

---