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ZINC BORATE

Zinc Borate, which enables plastic materials that are used actively in many areas of daily life to turn into stronger, durable and quality products, also protects these products against flame formation. Zinc Borate, which is also used as insulation material, makes pvc coatings, MDF, EVA products more durable. Zinc borate, which is widely used in sectors such as polymer, wood, textile, is a flame-retardant inorganic additive. With its flame retardant feature, which suppresses smoke and prevents corrosion, it is a raw material often used by many industries.

ZINC BORATE

CAS No. :  12513-27-8/12280-01-2
EINECS No.: 215-566-6

Synonyms:
ZINC BORATE; Boric acid, zinc salt; 10361-94-1; UNII-21LB2V459E; 21LB2V459E; Diboron zinc tetraoxide; Bonrex FC; zinc(II) borate; Flamtard Z 10; ZT (fire retardant); Alcanex FR 100; Alcanex FRC 600; Climax ZB 467; Firebrake ZB 2335; Borax 2335; ZB 467 Lite; DTXSID6091554; CTK0H1780; HSDB 1046; FRC 600; XPI 187; SZB 2335; ZSB 2335; EINECS 215-566-6; EINECS 238-763-9; ANW-19518; ZB 112; ZB 237; ZN 100; JS 9502; ZINC BORATE OXIDE 3.5 HYDRATE; FT-0726070; Q27253563; zn100; zb237; zb112; borax2335; Zinc borate; Firebrake ZB; ZincBoratePure; flameretardantzb; Borsure, Zinksalz; ZINC BORATE 3.5 HYDRATE; 7440-42-8; B; Boron; Boron, metallic; UNII-N9E3X5056Q; HSDB 4482; EINECS 231-151-2; N9E3X5056Q; MFCD00134034; Boron and compounds; boro; Boron-elemental; ZINC BORATE; Zinc Borate; Boron, elemental; Boron, Amorphous; Boron standard solution, for AAS, 1 mg-ml B in water; boracium; bore; boron atom; Boron powder; Boron Chelate; Boron Proteinate; BORaN; 5B; Boron Citrate Blend; Boron Picolinate Blend; Boron Krebs 5% 40M; Boron Glycinate 5% 40M; EC 231-151-2; Boron Trituration 1% 40M; KSC378S2P; boron citrate/aspartate/glycinate; DTXSID3023922; CHEBI:27560; CTK0H8670; CTK2H8927; MFCD00151272; AKOS015832923; AKOS030228749; Boron Citrate/Aspartate 5% 40M Bld; Boron, amorphous, powder, (submicron); DB11203; KS-0000117G; LS-45117; ZINC BORATE; Zinc Borate; SC-81633; Boron, >=95% (boron), amorphous powder; Boron, monofilament, 5m, diameter 0.1mm; 11129-12-7; Borate; ortho-borate ion; 14213-97-9; trioxidoborate(3-); trioxoborate(3-) ion; trioxoborate(III) anion; CHEBI:22908; CTK0H7368; DTXSID20931362; TRIISOPROPYL BORATE; 5419-55-6; Isopropyl borate; Triisopropoxyborane; Triisopropyl orthoborate; Triisopropoxyboron; Boron isopropoxide; Boric acid triisopropyl ester; Triisopropoxy borane; Boron triisopropoxide; tripropan-2-yl borate; triisopropylborate; Boric acid (H3BO3), tris(1-methylethyl) ester; tri-i-Propylborate; Triisopropoxy boron; Trisisopropoxyborane; Boric acid (H3BO3), triisopropyl ester; Isopropyl borate, ((C3H7O)3B); Boric acid, triisopropyl ester; Boric acid, tris(1-methylethyl) ester; tris(propan-2-yl) borate; NSC 9779; tri(isopropyl)borate; Boric acid triisopropyl; EINECS 226-529-9; MFCD00008872; UN2616; UNII-YWV817MXF3; BRN 1701469; YWV817MXF3; AI3-61082; Boric acid, (H3BO3), triisopropyl ester; DSSTox_CID_7598; DSSTox_RID_78523; ZINC BORATE; Zinc Borate; Triisopropyl borate, 98+%; DSSTox_GSID_27598; Triisopropyl borate, 98+%, AcroSeal(R); CAS-5419-55-6; triisopropyborate; triisopropyl borat; borax2335; Zinc borate; Firebrake ZB; ZincBoratePure; flameretardantzb; Borsure, Zinksalz; ZINC BORATE 3.5 HYDRATE; 7440-42-8; B; Boron; Boron, metallic; UNII-N9E3X5056Q; HSDB 4482; EINECS 231-151-2; N9E3X5056Q; MFCD00134034; Boron and compounds; boro; Boron-elemental; ZINC BORATE; Zinc Borate; Boron, elemental; Boron, Amorphous; Boron standard solution, for AAS, 1 mg-ml B in water; boracium; bore; boron atom; Boron powder; Boron Chelate; Boron Proteinate; BORaN; 5B; Boron Citrate Blend; Boron Picolinate Blend; Boron Krebs 5% 40M; Boron Glycinate 5% 40M; EC 231-151-2; Boron Trituration 1% 40M; KSC378S2P; boron citrate/aspartate/glycinate; DTXSID3023922; CHEBI:27560; CTK0H8670; CTK2H8927; MFCD00151272; AKOS015832923; AKOS030228749; Boron Citrate/Aspartate 5% 40M Bld; Boron, amorphous, powder, (submicron); DB11203; KS-0000117G; LS-45117; ZINC BORATE; Zinc Borate; SC-81633; Boron, >=95% (boron), amorphous powder; Boron, monofilament, 5m, diameter 0.1mm; 11129-12-7; Borate; ortho-borate ion; 14213-97-9; trioxidoborate(3-); trioxoborate(3-) ion; trioxoborate(III) anion; CHEBI:22908; CTK0H7368; DTXSID20931362; TRIISOPROPYL BORATE; 5419-55-6; Isopropyl borate; Triisopropoxyborane; Triisopropyl orthoborate; Triisopropoxyboron; Boron isopropoxide; Boric acid triisopropyl ester; Triisopropoxy borane; Boron triisopropoxide; tripropan-2-yl borate; triisopropylborate; Boric acid (H3BO3), tris(1-methylethyl) ester; tri-i-Propylborate; Triisopropoxy boron; Trisisopropoxyborane; ZINC BORATE; Boric acid, zinc salt; 10361-94-1; UNII-21LB2V459E; 21LB2V459E; Diboron zinc tetraoxide; Bonrex FC; zinc(II) borate; Flamtard Z 10; ZT (fire retardant); Alcanex FR 100; Alcanex FRC 600; Climax ZB 467; Firebrake ZB 2335; Borax 2335; ZB 467 Lite; DTXSID6091554; CTK0H1780; HSDB 1046; FRC 600; XPI 187; SZB 2335; ZSB 2335; EINECS 215-566-6; EINECS 238-763-9; ANW-19518; ZB 112; ZB 237; ZN 100; JS 9502; ZINC BORATE OXIDE 3.5 HYDRATE; FT-0726070; Q27253563


Zinc Borate

Zinc Borate, which enables plastic materials that are used actively in many areas of daily life to turn into stronger, durable and quality products, also protects these products against flame formation. Zinc Borate, which is also used as insulation material, makes pvc coatings, MDF, EVA products more durable. Zinc borate, which is widely used in sectors such as polymer, wood, textile, is a flame-retardant inorganic additive. With its flame retardant feature, which suppresses smoke and prevents corrosion, it is a raw material often used by many industries.
Safe Living Areas with Boron
Zinc Borate, helps to create safer living spaces by avoiding the formation of smoke and the release of toxic gases during possible fire incidents.  Zinc borates are often preferred as an important raw material in the polymer industry because of their high dehydration temperature. Zinc Borate, is widely used in textile and polymer sectors and in the wood protection sector to prevent the formation of fungi and insects. Produced from boron and boron products, Zinc Borate is involved in every aspect of life by combining its living spaces with safer, durable, long lasting and economical products.
In the event of possible fires, it helps to reduce the loss of life and property to minimum levels, thus provides time for the first intervention to fire. Zinc Borate, produced with boron and boron products that do not threaten human health, provides a more durable and long-lasting usage in application areas compared to chemical products.

Zinc borate is an inorganic compound, a borate of zinc. It is a white crystalline or amorphous powder insoluble in water. Its toxicity is low. Its melting point is 980 °C.
Variants of Zinc borate
Several variants of zinc borate exist, differing by the zinc/boron ratio and the water content:
Zinc borate Firebrake ZB (2ZnO·3 B2O3·3.5H2O), CAS number 138265-88-0
Zinc borate Firebrake 500 (2ZnO·3 B2O3), CAS number 12767-90-7
Zinc borate Firebrake 415 (4ZnO·B2O3·H2O), CAS number 149749-62-2
ZB-467 (4ZnO·6B2O3·7H2O), CAS number 1332-07-6
ZB-223 (2ZnO·2B2O3·3H2O), CAS number 1332-07-6
The hydrated variants lose water between 290–415 °C.
Uses of Zinc borate
Zinc borate is primarily used as a flame retardant in plastics and cellulose fibers, paper, rubbers and textiles. It is also used in paints, adhesives, and pigments. As a flame retardant, it can replace antimony(III) oxide as a synergist in both halogen-based and halogen-free systems.[2] It is an anti-dripping and char-promoting agent, and suppresses the afterglow. In electrical insulator plastics it suppresses arcing and tracking.
In halogen-containing systems, zinc borate is used together with antimony trioxide and alumina trihydrate. It catalyzes formation of char and creates a protective layer of glass. Zinc catalyzes the release of halogens by forming zinc halides and zinc oxyhalides.
In halogen-free system, zinc borate can be used together with alumina trihydrate, magnesium hydroxide, red phosphorus, or ammonium polyphosphate. During burning the plastics, a porous borate ceramics is formed that protects the underlying layers. In presence of silica, borosilicate glass can be formed at plastic burning temperatures.[3]
Zinc borate is used in polyvinyl chloride, polyolefins, polyamides, epoxy resins, polyesters, thermoplastic elastomers, rubbers, etc. It is also used in some intumescent systems.
Zinc borate has synergistic effect with zinc phosphate or barium borate as a corrosion inhibitor pigment.
Zinc borate acts as a broad-spectrum fungicide in plastics and wood products.
Zinc borate can be used as a flux in some ceramics. In electrical insulators it improves the ceramics properties.
Nanopowder zinc borate can be used for the applications above, and also for improving the frictional properties of lubricating oils.

Zinc borate appears as a white powder of variable composition. (typically 45% ZnO, 34% B2O3 and 20% H2O). Slightly soluble in water. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. It is used as a fungus and mildew inhibitor, to fire proof textiles, and for other uses.
For zinc borate (USEPA/OPP Pesticide Code: 128859) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses.
Zinc borates ... are used on an industrial scale as fire-retardant synergists for polymers, as preservatives for engineered wood products and wood-plastic composites, and as in-can preservatives, and as film fungicides in coatings /Zinc borates/
Zinc borate ... (4ZnO.B2O3.H2O) ... is used as a fire retardant in polymers requiring high processing temperatures
Zinc borates can be used alone, although it is not as effective in increasing flame resistance as when used in combination with other halogen synergists such as antimony oxide ... also used with alumina trihydrate to form a glass-like substance that inhibits polymer degradation /Zinc borates/
Zinc borate was shown to be an eye irritant producing mild conjunctivitis in albino rabbits.
Zinc borate is designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act and further regulated by the Clean Water Act Amendments of 1977 and 1978. These regulations apply to discharges of this substance. This designation includes any isomers and hydrates, as well as any solutions and mixtures containing this substance.
GENOTOXICITY/ In the Salmonella/microsomal Assay (Ames Bioassay) for bacterial mutagenic activity, zinc borate did not elicit any mutagenic response in Salmonella tester strains when tested either with or without a metabolic activation system.
OTHER TOXICITY INFORMATION/ In a dermal sensitization study involving guinea pigs, zinc borate showed no evidence of /sensitization/.
Zinc borate was shown to be an eye irritant producing mild conjunctivitis in albino rabbits.
Corrosivity in Albino Rabbits - The Primary Irritation Index of zinc borate in rabbits was found to be 0. Therefore, it is not considered to be an irritant or corrosive.
BIRDS and MAMMALS/ In avian dietary studies, the LC50 value of zinc borate in the mallard ducklings (Anas platyrhynchos) is estimated to be greater than 5,620 ppm. No mortality occurred in either the control or treated groups. A slight reduction in body weight was observed at the 6,520 ppm concentration during the exposure period. There was no effect on feed consumption at any concentration tested.
AQUATIC SPECIES/ The acute toxicity of zinc borate to bluegill sunfish (Lepomis macrochirus) was tested under static conditions at mean concentrations of 94, 137, 182, 248, and 335 ppm. The 96 hr LC50 for bluegill sunfish was shown to be greater than 335 ppm. These results indicate that zinc borate is practically nontoxic to the fish species tested.
According to the 2006 TSCA Inventory Update Reporting data, the number of persons reasonably likely to be exposed in the industrial manufacturing, processing, and use of zinc borate is 100 to 999; the data may be greatly underestimated(1).
NIOSH (NOES Survey 1981-1983) has statistically estimated that 20,343 workers (4,266 of these were female) were potentially exposed to zinc borate in the US(1). Occupational exposure to zinc borate may occur through inhalation and dermal contact with this compound at workplaces where zinc borate is produced or used(SRC).

There is limited information in the literature on the toxicity of zinc borate. Zinc borate readily breaks down in the stomach to zinc oxide (ZnO) and boric acid (H3BO3). Therefore, this chapter reviews the physical and chemical properties, toxicokinetics, toxicological, epidemiological, and exposure data on both those compounds. When data on zinc oxide are lacking, data on other zinc compounds are reviewed. According to the International Programme on Chemical Safety (IPCS), at low concentrations and under the same conditions, an equivalent amount of boron as boric acid or borax has similar chemical and toxicological properties (IPCS 1998). Therefore, data from boric acid and borax are considered in this chapter. Regardless of the zinc or boron compound of exposure, body burdens are measured as the concentration of the element (zinc or boron), and are discussed as such in this review. Doses are given in boron and zinc equivalents for comparison between different zinc and boron compounds.
The subcommittee used the toxicity, toxicokinetic, and exposure data on those compounds to characterize the health risk from exposure to zinc borate. The subcommittee also identified data gaps and recommended research relevant for determining the health risk from exposure to zinc borate.
OCCURRENCE AND USE
Zinc borate is typically composed of 45% ZnO and 34% boric anhydride (B2O3), with 20% water of hydration. Zinc borate is used as a flame retardant in conjunction with other chemicals, including antimony trioxide, magnesium hydroxide, alumina trihydrate, and some brominated flame retardants. Zinc borate is used as a flame retardant on commercial furniture, draperies, wall coverings, and carpets (R.C.Kidder, Flame Retardant Chemical Association, unpublished material, April 21, 1998). In addition, zinc borate is used as a fungicide.
Zinc oxide is used as a pigment in paint, cosmetics, and dental and quick drying cements. Therapeutically, zinc oxide is used as an astringent and as a topical protectant.
Boric acid is used in enamels, porcelain, soaps, cosmetics, and as an insecticide. Therapeutically, boric acid is used as an astringent and an antiseptic.
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TOXICOKINETICS
Absorption
Zinc Borate
No studies were identified that investigate the toxicokinetics of zinc borate following dermal, inhalation, or oral exposure.
Metabolism and Distribution
Zinc Borate
Zinc borate is metabolized to zinc oxide and boric acid prior to being absorbed.
Excretion
Zinc Borate
No data were identified that investigated the excretion of zinc borate in humans or animals following any route of exposure.
Irritation and Sensitization
Zinc Borate
Zinc borate produced only mild conjunctivitis in albino rabbits in the eye irritation test and is not considered to be an irritant or corrosive (U.S. Borax 1996).
Zinc borate was negative in the guinea pig sensitization test (U.S. Borax 1996).
Systemic Effects
Zinc Borate
The LD50 in male and female albino rabbits following dermal exposure to zinc borate is estimated to be >10 g/kg (U.S. Borax 1996).
Other Systemic Effects
No studies were found that investigated the immunological, neurological, reproductive, developmental, or carcinogenic effects of zinc borate, zinc oxide, or boric acid following dermal exposure in humans or experimental animals.
Inhalation Exposure
No data were found on toxic effects of zinc borate following inhalation exposure. Data on the toxic effects of zinc oxide and boric acid following inhalation exposure are discussed below.
Noncancer
Dermal Assessment
There are inadequate dermal toxicity data on zinc borate, zinc oxide, or boric acid to derive a risk value for dermal exposure.
Inhalation RfC
There are inadequate inhalation toxicity data on zinc borate, zinc oxide, or boric acid to derive an inhalation RfC.
Oral RfD
There are inadequate oral toxicity data on zinc borate to derive an oral RfD. However, zinc borate readily breaks down in the stomach to zinc oxide and boric acid. The subcommittee used the available dose-response data for both compounds to derive their RfDs and selected the more conservative RfD of the two values to characterize the health risk of zinc borate.

Zinc Borate
In order to derive an oral RfD for zinc borate from the RfDs for zinc compounds and boric acid, the relative contributions of zinc and boron to zinc borate were determined. Boron comprises approximately 11.3% (w/w) of zinc borate (3ZnO:2B2O3) (Lide 1991–1992). The RfD for zinc borate, based on the RfD for boron (0.34 mg boron/kg-d), would be approximately 3.0 mg zinc borate/kg-d. Zinc comprises approximately 51.2% (w/w) of zinc borate (3ZnO:2B2O3). The RfD for zinc borate, based on the RfD for zinc (0.3 mg zinc/kg-d), would be approximately 0.6 mg zinc borate/kg-d.
The oral RfD for zinc borate based on zinc is more conservative than the RfD for zinc borate based on boron. Therefore, the overall oral RfD for zinc borate is 0.6 mg zinc borate/kg-d, based on the RfD for zinc.
The subcommittee also considered the possibility of additive or synergistic effects between zinc and boron when assessing the risks associated with exposure to zinc borate. The main effects of boron are reproductive and developmental effects. Zinc has been shown to have reproductive effects in animals, but only at extremely high doses (≥200 mg Zn/kg-d). Effects other than reproductive and developmental have only been seen following exposure to boric acid at very high doses (≥1,000 ppm-d). The subcommittee concluded that additive or synergistic effects are not expected because of the lack of target overlap.
The subcommittee's confidence in the zinc RfD is medium. The lack of data on the parent compound makes the overall confidence in the oral RfD (0.6 mg zinc borate/kg-d) low.

Cancer
The potential carcinogenicity of zinc borate, zinc oxide, and boric acid cannot be determined because of inadequate carcinogenicity data from any route of exposure.
Noncancer
Dermal Exposure
The assessment of noncancer risk by the dermal route of exposure is based on the scenario described in Chapter 3. This exposure scenario assumes that an adult spends 1/4th of his or her time sitting on furniture upholstery treated with zinc borate, that 1/4th of the upper torso is in contact with the upholstery, and that clothing presents no barrier. Zinc borate is considered to be ionic, and is essentially not absorbed through the skin. However, to be conservative, the subcommittee assumed that ionized zinc borate permeates the skin at the same rate as water, with a permeability rate of 10−3 cm/hr (EPA 1992). Using that permeability rate, the highest expected application rate for zinc borate (2 mg/cm2), and Equation 1 in Chapter 3, the subcommittee calculated a dermal exposure level of 6.3×10−3 mg/kg-d. The oral RfD for zinc borate (0.6 mg/kg-d; see Oral RfD in Quantitative Toxicity section) was used as the best estimate of the internal dose for dermal exposure. Dividing the exposure level by the oral RfD yields a hazard index of 1.0×10−2. Thus it was concluded that zinc borate used as a flame retardant in upholstery fabric is not likely to pose a noncancer risk by the dermal route.
Inhalation Exposure
Particulates
The assessment of the noncancer risk by the inhalation route of exposure is based on the scenario described Chapter 3. This scenario corresponds to a person spending 1/4th of his or her life in a room with low air-change rate (0.25/hr) and with a relatively large amount of fabric upholstery treated with zinc borate (30 m2 in a 30-m3 room), with this treatment gradually being worn away over 25% of its surface to 50% of its initial quantity over the 15-yr lifetime of the fabric. A small fraction, 1%, of the worn-off zinc borate is released into the indoor air as inhalable particles and may be breathed by the occupant. Equations 4 through 6 in Chapter 3 were used to estimate the average concentration of zinc borate present in the air. The highest expected application rate for zinc borate is about 2 mg/cm2. The estimated release rate for zinc borate is 2.3×10−7/d. Using those values, the estimated time-averaged exposure concentration for zinc borate is 0.19 µg/m3.
Although lack of sufficient data precludes deriving an inhalation RfC for zinc borate, the oral RfD (0.6 mg zinc borate/kg-d; see Oral RfD in Quantitative Toxicity section), which represents a conservative estimate, was used to estimate an RfC of 2.1 mg/m3 (see Chapter 4 for the rationale).
Division of the exposure concentration (0.19 µg/m3) by the estimated RfC (2.1 mg/m3) results in a hazard index of 9.1×10−5. Therefore, the subcommittee concluded that, under the worst-case exposure scenario, exposure to zinc borate particles from its use as an upholstery fabric flame retardant is not likely to pose a noncancer risk.
Vapor
In addition to the possibility of release of zinc borate in particles worn from upholstery fabric, the subcommittee considered the possibility of its release by evaporation. However, because of zinc borate's negligible vapor pressure at ambient temperatures, the subcommittee concluded that exposure to zinc borate vapors from its use as an upholstery fabric flame retardant is not likely to pose a noncancer risk.
Oral Exposure
The assessment of the noncancer risk by the oral exposure route is based on the scenario described in Chapter 3. The exposure assumes a child is exposed to zinc borate through sucking on 50 cm2 of fabric, backcoated with zinc borate, daily for two yr, one hr/d. The highest application rate for zinc borate is 2 mg/m2. A fractional rate (per unit time) of zinc borate extraction by saliva is estimated as 0.001/d, based on leaching of antimony from polyvinyl chloride cot mattresses (Jenkins et al. 1998). Using those assumptions in Equation 15 in Chapter 3, the average oral dose rate was estimated to be 0.00017 mg/kg-d. Division of that exposure estimate (0.00017 mg/kg-d) by the oral RfD (0.6 mg/kg-d; see Oral RfD in Quantitative Toxicity Assessment Section) results in a hazard index of 2.8×10−4. Therefore, under the worst-case exposure assumptions, zinc borate, used as a flame retardant in furniture-upholstery fabric, is not likely to pose a noncancer risk by the oral route of exposure.
Cancer
There are inadequate data to characterize the carcinogenic risk from exposure to zinc borate, zinc oxide, or boric acid from any route of exposure.
DATA GAPS AND RESEARCH NEEDS
There are little toxicity data available for zinc borate. Once in the body, zinc borate readily breaks down to zinc oxide and boric acid. There are no chronic studies investigating the carcinogenicity of zinc oxide and boric acid. There are no studies that measured exposure levels from the use of zinc borate as a flame retardant in upholstery furniture fabric. However, there are extensive databases on the toxicity of zinc oxide and boric acid, and the hazard indices for zinc borate, based on those data, are less than one for all three routes of exposure, using the subcommittee's conservative assumptions. Therefore, the subcommittee concluded that no further research is needed to assess the health risks from the use of zinc borate as a flame retardant.

Zinc borate is primarily used as a flame retardant in plastics and cellulose fibers, paper, rubbers and textiles. It is also used in paints, adhesives, and pigments. As a flame retardant, it can replace antimony trioxide as a synergist in both halogen-based and halogen-free systems. It is an anti-dripping and char-promoting agent, and suppresses the afterglow. In electrical insulator plastics it suppresses arcing and tracking.
In halogen-containing systems, zinc borate is used together with antimony trioxide and alumina trihydrate. It catalyzes formation of char and creates a protective layer of glass. Zinc catalyzes the release of halogens by forming zinc halides and zinc oxyhalides.
In halogen-free system, zinc borate can be used together with alumina trihydrate, magnesium hydroxide, red phosphorus, or ammonium polyphosphate. During burning the plastics, a porous borate ceramics is formed that protects the underlying layers. In presence of silica, borosilicate glass can be formed at plastic burning temperatures.
Zinc borate is used in polyvinyl chloride, polyolefins, polyamides, epoxy resins, polyesters, thermoplastic elastomers, rubbers, etc. It is also used in some intumescent systems.
Zinc borate has synergistic effect with zinc phosphate or barium borate as a corrosion inhibitor pigment.
Zinc borate acts as a broad-spectrum fungicide in plastics and wood products.
Zinc borate can be used as a flux in some ceramics. In electrical insulators it improves the ceramics properties.
Nanopowder zinc borate can be used for the applications above, and also for improving the frictional properties of lubricating oils.

Characteristics
Zinc Borate is a Boron based flame retardant compatible with many polymeric matrices. It is effective both in the solid phase and in the gas phase and its strong smoke suppressing action, helps to improve time of rescue in case of fire.
Zinc Borate is a multifunctional flame retardant:
promotes the formation of a protective vitreous layer and of a strong char layer, which reduces the formation of toxic and irritant smoke during the fire
It looses its water of hydration at temperatures above 290°C, cooling the front of the flames and subtracting energy to the fire
It acts as a synergist in conjunction with halogenated compounds, so that lower loadings of halogenated flame retardant additives are needed
It shows a strong synergic effect with antimony trioxide; in presence of alumina trihydrate (ATH) the synergic effect is enhanced
It improves resistance against electrical degradation: high anti-arcing and anti-tracking indexes
It is an afterglow suppressant.
Uses
Zinc borate is prepared as an insoluble double salt from water-soluble zinc and boron compounds. Compounds having varying amounts of zinc, boron, and water of hydration are available. The ratio of these components affects the temperature at which the flame-inhibiting powers are activated, as well as the temperature at which they can be processed. Zinc borates can either be used alone or in combination with other halogen synergists, such as antimony oxide. In some instances zinc borate is also used with alumina trihydrate to form a glass-like substance that inhibits polymer degradation.
Uses
Medicine, fireproofing textiles, fungistat and mildew inhibitor, flux in ceramics.
Application
zinc borate is primarily used as a flame retardant in plastics and cellulose fibers, paper, rubbers and textiles. It is also used in paints, adhesives, and pigments. As a flame retardant, it can replace antimony trioxide as a synergist in both halogen-based and halogen-free systems. It is an anti-dripping and char-promoting agent, and suppresses the afterglow. In electrical insulator plastics it suppresses arcing and tracking.
In halogen-containing systems zinc borate is used together with antimony trioxide and alumina trihydrate. It catalyzes formation of char and creates a protective layer of glass. Zinc catalyzes the release of halogens by forming zinc halides and zinc oxyhalides.
In halogen-free systems, zinc borate can be used together with alumina trihydrate, magnesium hydroxide, red phosphorus, or ammonium polyphosphate. When burning the plastics, a porous borate ceramic is formed that protects the underlying layers. In presence of silica, borosilicate glass can be formed at plastic burning temperatures.
As the partial, or completely EPA approved substitute for containing halogen and other flame retardants, zinc borate is being directly applied to a wide range of plastics and rubber processing such as PVC, PE, PP, and to enhance polyamide, PVC resin, polyphenylene ethylene, epoxy resin, polyester resin, acid ethylene and natural rubber, styrene butadiene rubber, and chloroprene rubber. It can also be applied to the production of paper, fiber fabric, decorative panels, floor leather, wallpaper, carpet, ceramic glaze, fungicides, and paint production to improve flame retardant performance.
Production Methods
Zinc borate (2ZnO·3B2O3·3.5H2O) in general is produced with the reaction between zinc oxide and boric acid. Boric acid is solved in water between temperatures 95ºC and 98ºC and zinc oxide and seed crystal of 2ZnO·3B2O3·3.5H2O is added to this solution at a certain stoichiometric ratio. The reaction continues for a while by mixing and the zinc borate formed is filtered, dried and ground. The boric acid solution is fed to the system as reflux.
Industrial uses
zinc borate (2ZnO-3B2Ovl5H2O) has a greater flame retardancy than borates used alone.
Zinc compounds perform most of their flame retardant function in the condensed phase. Zinc is used with boron in the form of zinc borate, and with molybdenum in the form of zinc molybdate. Zinc borate can also be used as a flame retardant and smoke suppressant with different polymers. In the case of zinc borate, 2ZnO.3B203.3.5H20, water given off can promote the formation of a cellular char which can act as a good insulator in protecting the underlying polymer or substrate. Moore studied the effects of zinc borate on smoke reduction and flame retardancy of PVC. He reported that smoke generation can be suppressed by over 40% by proper combination of additives without an adverse effect on flame retardancy. The use of zinc borate as a flame retardant and smoke suppressant alone or with other additives, e.g. Sb203, or AI(OH)3, has found wide application in the plastics industry.

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