Study On Phthalic And Stearic Acid （Poly） Glycerides And Their Metal Salts As Lubricants For PVC

Poly（vinyl chloride）（PVC）is an important thermoplastic with unique performance and wide application.However,because of its strong polarity,PVC has some processability problems during thermoplastic processing,such as high friction heat generation,high melt viscosity and serious adhesion to the metal surface of processing equipment.Therefore,the lubricant which can reduce friction heat generation,melt viscosity and melt adhesion to the metal surface of processing equipment is a necessary additive for PVC thermoplastic processing.At present,although there are many PVC lubricants available in the market,they have the shortcoming of low comprehensive performance.Therefore,in order to provide some research ideas and experimental basis for the development of PVC lubricants with high comprehensive properties,this dissertation explored and synthesized phthalic and stearic acid（poly）glycerides and their metal salts with various functional groups（carboxyl,hydroxyl,ester,etc.）,and systematically tested their lubricating properties（including resin lubricating properties and metal lubricating properties）and main related properties（including pressure-out property,frost-spraying property,fogging property and thermal stability）as PVC lubricants,then analyzed and studied the gradual change law of properties and preliminarily discussed the principle.The main research results were as follows:1.Phthalic acid monohydric and monostearate（poly）glycerides with different phthalic acid monoesterification numbers can be quantitatively synthesized by directly heating and stirring phthalic anhydride and monostearate（poly）glycerides with a stoichiometric ratio at an appropriate temperature for reaction for a certain time,wherein the highest phthalic acid monoesterification numbers of glyceryl monostearate,triglycerides,hexapolyglycerols and decapolyglycerols can reach 2,3,3 and 4 respectively under the existing conditions.The corresponding metal salt can be synthesized by heating and stirring the stoichiometric ratio of phthalic acid monohydric and monostearate（poly）glycerides and metal（magnesium,calcium,strontium and barium）oxide or hydroxide in an aqueous medium at a proper temperature until the mother solution is neutral.2.Like the parent（poly）glyceryl monostearate,the synthesized phthalic acid monohydric and monostearate（poly）glycerides belongs to resin internal lubricants,but their properties are all higher than those of parent（poly）glyceryl monostearate,and many varieties are close to or even higher than stearic acid（the existing PVC internal lubricant with the strongest internal lubricant in resin）,among which double phthalic acid monohydric and monostearate（poly）glycerides is 1.44 times of stearic acid;Their properties show a gradual law of increasing first and then decreasing with the increase of glycerol polymerization degree or phthalic acid monoester number.The reason why phthalic acid monohydric and monostearate（poly）glycerides has such characteristics lies in that replacing the hydroxyl group of mono-stearic acid（poly）glyceryl monostearate with mono-hydrogen phthalate can make its cohesion closer to PVC.The synthesized alkaline earth metal salt of phthalic acid monohydric and monostearate（poly）glycerides has that functions of both internal resin lubricant and external auxiliary resin lubricant,and the external lubrication performance of most auxiliary resin is higher than that of calcium stearate（commonly used external auxiliary resin lubricant）,among which the performance of magnesium salt of mono-hydro-monostearate is 2.67 times of that of calcium stearate;The external lubricating properties of their auxiliary resins show a gradual law of first decreasing and then increasing with the increase of alkaline earth metal ion radius,glycerol polymerization degree or phthalic acid monoester number.It is speculated that metal soaps with different metal ions,polymerization degrees or esterification numbers can stabilize the interface between PVC and main effect resin external lubricant to varying degrees.3.The research results of extrusion,frosting,fogging and thermal stability of the synthesized phthalic acid monohydric and monostearate（poly）glycerides and their alkaline earth metal salts are as follows:（1）Although stearic acid,a commonly used lubricant in resin,does not press out during processing,it is seriously frosted.Although calcium stearate,a commonly used external lubricant for auxiliary resin,does not spray frost,it is pressed out seriously during processing.However,the phthalic acid monohydric and monostearate（poly）glycerides and their alkaline earth metal salts synthesized in this thesis do not produce observable pressure precipitation and frost spray,and it should be that the molecule contains ester group,hydroxyl group and ether group,which makes it compatible with PVC.（2）The fogging property of phthalic acid monohydric and monostearate（poly）glycerides is low,all of which are obviously lower than that of stearic acid.It should be that the molecule contains ester group,hydroxyl group and ether group,which makes it compatible with PVC.However,the fogging property of phthalic acid monohydric and monostearate（poly）glycerides is lower than that of parent mono-stearic acid（poly）glyceride.It should be that the hydroxyl group of mono-stearic acid（poly）glyceride is replaced by mono-hydrogen phthalate,which can make its cohesion closer to PVC,so it has better compatibility with PVC.Compared with the corresponding esters,the fogging property of alkaline earth metal salt of phthalic acid monohydric and monostearate（poly）glycerides is higher,which should be caused by the strong polar carboxylate group.The fogging property of alkaline earth metal salt of phthalic acid monohydric and monostearate（poly）glycerides is lower than that of the corresponding stearate,and it should be that the molecule contains ester group,hydroxyl group and ether group to make it more compatible with PVC.（3）The long-term thermal stability of phthalic acid monohydric and monostearate（poly）glycerides is stronger than that of the corresponding parent mono-stearic acid（poly）glyceride and the existing common internal lubricant stearic acid.It should be a plurality of hydroxyl groups of phthalic acid monohydric and monostearate（poly）glycerides,which can chelate and coordinate with the metal chloride produced by the heat stabilizer mercaptan organotin,thus weakening its catalytic effect on hydrogen chloride removal of PVC.Moreover,the hydroxyl group of（poly）glyceryl monostearate should be replaced by monohydrogen phthalate,which can make its chelating coordination with metal chloride stronger.The long-term thermal stability of most metal salts of phthalic acid monohydric and monostearate（poly）glycerides is stronger than that of corresponding alkaline earth metal salts of stearic acid and corresponding phthalic acid monohydric and monostearate（poly）glycerides.It should be because it has many hydroxyl and carboxylate ions,which not only have chelating coordination,but also can neutralize the hydrogen chloride produced by PVC degradation and inhibit its catalytic effect on PVC degradation,thus showing stronger long-term thermal stability.