Study On Surface Modification And Application Of Calcium Carbonate As A Coating Filler

Calcium carbonate,as common coating filler,has the characteristics of high whiteness,non-toxicity and low price.It is often used in rubber,papermaking,chemical fiber,textile,coating and other industries to improve the physical properties,chemical properties,and dimensional stability of polymer.At present,there are still a lot of problems in the use of calcium carbonate as the filler of wet coating fabric in the production of traditional trademark belt companies,such as poor ink absorption and high pH.In order to solve these problems,this paper applies surface modification of calcium carbonate by using double-site stearic acid modifier,sodium stearate,sodium oleate and oleic acid,and applies modified calcium carbonate to the wet coating of polyamide.In the coating,the effect of different modifiers on the performance of polyamide wet coating was investigated,and the calcium carbonate coating filler which satisfies the good performance of the coated fabric was selected.By comparing the FTIR,NMR and MS spectra of glycerol monostearate and synthetic products,the synthesis product of monostearate and maleic anhydride was determined to be double site stearic acid.The surface modification effect of calcium carbonate was characterized by activation and sedimentation volume.The mechanism of surface modification of calcium carbonate by sodium stearate and double stearic acid was investigated by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The results showed that the optimum process of calcium carbonate modified by sodium stearate was that the dosage of sodium stearate was 15%,the modification temperature was 60 ?,and the modification time was 6 hours,the activation degree is 97%,the sedimentation volume is 3.78 mL,the comprehensive modification effect is the best;When the dosage of double site stearic acid is 20%,the activation degree is 95.38 and the sedimentation volume is 4.08 mL,the overall modification effect is the best.It was found that the surface modification of calcium carbonate by sodium stearate was poor,while the double site stearic acid formed an organic coating layer on the surface of calcium carbonate,which was not easy to be removed by washing solution during the preparation process,so that the lipophilicity and dispersity of calcium carbonate be improved.Sodium oleate was used to directly modify the surface of calcium carbonate,and oleic acid was used to modify the surface of calcium carbonate in situ.The modification effect was characterized by activation degree and sedimentation volume.The mechanism of direct modification of calcium carbonate by sodium oleate and in situ synthesis of calcium carbonate by oleic acid was investigated by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The results showed that the optimum process for the modification of calcium carbonate by sodium oleate was as follows: the dosage of sodium oleate was 15%,the modification temperature was 60 ?,and the modification time was 6 h,the activation degree is 95%,the sedimentation volume is 3.05 mL,the overall modification effect is the best.The crystal form of the prepared calcium carbonate has not changed,and sodium oleate can be coated on the surface of calcium carbonate,thus avoiding the agglomeration of calcium carbonate particles.When the amount of oleic acid is 15%,the activation degree is 99%,the sedimentation volume is 4.18 mL,and the modification effect is the best.The crystal form of calcium carbonate is mainly composed of spheroidal type,and the surface of calcium carbonate is coated with oleic acid,and the surface of calcium carbonate is uniformly coated with oleic acid.The chemical binding of-OH on the surface of calcium carbonate to the-COOH on oleic acid molecular chain was observed.By comparing the properties of polyamide coated products prepared from different modified calcium carbonates,the effects of different modified calcium carbonates on the properties of polyamide wet coated products were investigated.The results showed that the elongation at break was 29.21% and 25.46%,respectively,and the initial modulus of elasticity was less than 0.0435 MPa of untreated calcium carbonate.The surface of polyamide wet-process coating prepared by in-situ synthesis of calcium carbonate with oleic acid is smooth and porous.The ink contact angle is 31.93�,the ink length of the coated fabric is 20.20 mm,and the pH is 7.27.The pore distribution of polyamide wet coating film prepared by double site stearic acid modified calcium carbonate is uniform,the contact angle of ink is 38.15 �,and the ink length of coated fabric is 16.50 mm,and the pH value is 7.33.The results show that compared with the wet coating products of polyamide prepared by unmodified calcium carbonate,the ink absorption properties of the above two modified calcium carbonate coatings are significantly improved,and the pH value is obviously decreased,which is more in line with the requirements of textile safety standards.In this paper,the effect and mechanism of double site stearic acid,sodium stearate and oleic acid on the modification of calcium carbonate and the effect of different modified calcium carbonate on the properties of polyamide wet coating were studied systematically.The ink absorption of calcium carbonate as coating filler was improved,and the pH value was reduced,which provided a theoretical basis and guidance for the industrial production of trademark fabrics with wet coating.