Study On Preparation, Structure And Properties Of Rosin-Acrylate Hybrid Latexes

The rosin is a major kind of forest chemicals with annual output of about 800000 tons inChina. Its special characteristics on molecular structure bring it some distinct properties oninsulation, adhesion, emulsification and tackifying ability, etc. The reactive groups such ascarboxyl and conjugated double bonds on its molecules can be further modified to preparemany kinds of fine chemicals and polymer materials with distinct properties and high addedvalue. The acrylate polymers are an important series of polymer materials and widely used inpacking, adhesive and coating industries. The mini-emulsion polymerization is an effectivemethod to prepare polymer composites. The general ideas of this paper is to prepare polymercomposite emulsions of modified rosins and acrylates with mini-emulsion polymerizationmethod, and to discover the relations between their preparation, structure and properties, andfinally to provide theoretical basis to the deep utilization of rosin and to the development ofnew polymer materials from natural renewable resources. The main research results weredescribed as the below:1. Mini-emulsion polymerization of hydrogenated rosin/acrylateIn the mini-emulsion polymerization, the monomers are dispersed in advance intonano-meter sized liquid beads, which are kept stable by the action of stabilization agents. Thenthe monomers begin to polymerize by the initiation of initiators. During the polymerization, theparticle size can be kept unchanged at a certain level, and the composition of beads can also bekept unchanged, so the resulted polymer particles is corresponding to the monomer beads at theideal situations. In this paper, the stable composite emulsion of poly (methyl methacrylate)(PMMA) containing hydrogenated rosin was prepared with mini-emulsion polymerization. Theinfluence of the amount of hydrogenated rosin on the particle size and the conversionpercentage of monomers was investigated. The experimental results indicated that, thehydrogenated rosin could play a role of stabilization for the monomer liquid beads of methylmethacrylate (MMA), although its performance was not as good as that of n-cetane forstabilizing the mini-emulsion beads. The size of liquid beads of MMA monomers containinghydrogenated rosin was close to the polymer particles as final products, and the new polymer particles produced in the polymerization accounted only for a small part. The introduction ofhydrogenated rosin into PMMA resulted in the decreased molecular weight and lowered glasstransition temperature. The thermal analysis results indicated that the hydrogenated rosin hadgood compatibility with PMMA, and could act as the plastification and tackifying agents.2. Preparation and analysis of radically polymerizable rosin derivativesThe preparation of rosin derivatives with potential of radical polymerization was the firststep to investigate the co-polymerization of rosin derivatives with acrylates. In this paper,firstly a series of acryloxyl derivatives were synthesized from the dehydrogenated abietic acid,a main composition of disproportionated rosin, through acyl chloridation and esterification.The derivatives included the (β-acryloxyl ethyl) esters of dehydrogenated abietie acid,(β-methacryloxyl ethyl) esters of dehydrogenated abietic acid and (β-methacryloxyl propyl)esters of dehydrogenated abietic acid. The above products were identified with IR, GC-MS andLC methods.Secondly, the acrylate derivatives of disproportionated rosin were synthesized by acylchloridation and esterification. The changing of characteristic groups during the reaction wasanalyzed with IR. The influence of reaction time, temperature and material ratio on theconversion of carboxyl groups into acyl chloride was investigated. The ¹³C NMR analysis tothe carbon atoms on carbonyl group confirmed the conversion of above groups. Thecompositions of raw material and products were identified with GC-MS, the results indicatedthat the products were composed of (β-acryloxyl ethyl) esters of dihydropimaric acid anddehydrogenated abietic acid, and their relative amounts was consistent with the amount ofdihydropimaric acid and dehydrogenated abietic acid in the disproportionated rosin.Thirdly, the acrylic rosin was synthesized by the addition reaction from gum rosin andacrylic acid. The levo-pimaric acid was converted into acrylic pimarie acid throughDiels-Alder addition with acrylic acid. The abietic-type acids in the gum rosin were inisomerization balance under high temperature, and the abietic acid and palstric acid would beconverted into levo-pimaric acid and reacted in the later type. The experimental results alsoindicated that the addition reaction could not be completed thoroughly, and there were someresidue abietic-type acids. There were two kinds of addition products. The carboxyl group andisopropyl group on the six-carboned ring could be at both meta and para positions, and the para product was dominated (80%). The ester product with two acryloxyl groups could besynthesized from acrylic rosin, which has two carboxyl groups in its major composition acrylicpimaric acid. So the bio (β-acryloxyl ethyl) esters of acrylic rosin (AR-2-HEA) with majorcomposition of bio- (β-acryloxyl ethyl) esters of acrylic pimaric acid were also prepared through acylchloridation and esterification. The analysis results of GC-MS and LC confirmed the synthesisof above products.3. Polymerization properties and reaction dynamics of polymerizable rosin derivativesAs a new kind of monomers, there had not any reports on the polymerization propertiesand reaction dynamics of above polymerizable rosin derivatives. In this paper, the DSC methodwas used to investigate the reaction activation energy and dynamics of homo-polymerization ofAR-2-HEA. The thermal effects of even temperature-rising reaction process and isothermalreaction process were analyzed with different dynamic models. The activation energy ofhomo-polymerization of AR-2-HEA was 105.9～107.4KJ/mol. The dynamic equations wererespectively as the below: dα/dt=1.86×10¹⁴×exp(-107.4×10³/RT)(1-α)^0.944 dα/dt=1.63×10¹⁴exp(-106.4×10³/RT)α^0.1435(1-α)^1.098 dα/dt=1.48×10¹⁴×exp(-105.9×10³/RT)(1-α)^1.05The results of synchronous TG-DSC analysis on the AR-2-HEA and (β-acryloxyl ethyl)ester of disproportionated rosin (DPR-2-HEA) indicated that, the heat resistance ofhomopolymer of AR-2-HEA was improved by a little due to the relatively high molecularweight of acrylic rosin acid. But the heat resistance of homopolymer of DPR-2-HEA wasimproved with a relatively large range.In the research of mini-emulsion copolymerization of DPR-2-HEA and MMA, it wasfound that the DPR-2-HEA had stronger stabilization effect on the mini-emulsion thanhydrogenated rosin. The dosage of initiator had apparent influence on the polymerization rate,and the higher the dosage of initiator, the quicker the reaction rate, and the less fluctuation of particle size during the polymerization. The GPC results showed there were goodeopolymerization between MMA and DPR-2-HEA. The glass transition temperature ofhomopolymer of DPR-2-HEA was 281K, so the glass transition temperature of its copolymerwith MMA gradually descended following the increase of amount of DPR-2-HEA. Thecopolymer initiated by APS could dissolve completely, but some crosslinked products wereobtained due to the transition of initiator to macromolecular chains when the copolymerizationwas initiated with BPO. The copolymerization process of AR-2-HEA with MMA was similar tothat of DPR-2-HEA, but AR-2-HEA could enhance the crosslinking degree of copolymer,which resulted in the high heat resistance of such copolymer.4. Preparation of composite emulsions of rosin derivatives/acrylates and their propertiesFor the industrial application of composite emulsions of rosin derivatives/acrylates, in thispaper the polymer emulsions with solid content of 50% and viscosity of below 200 nPaS wereprepared through the mini-emulsion polymerization. The resulted polymer emulsion had anaverage particle size of 400-1000 nm with wide distribution. The pressure-sensitive adhesiveemulsion with solid content of 50% was prepared through the copolymerization ofDPR-2-HEA with acrylates. The research results indicated that, when the polymerization wasinitiated with APS, the polymer's durative adhesion declined seriously but the initiativeadhesion and 180°peel strength were improved, because the polymer's molecular weight wasreduced sharply due to the chain-transition. When BPO was used as the initiator, the transitionof radicals to the macromolecular chains resulted in the polymer's partial crosslinking, whichcompensated the effect of declined molecular weight. The durative adhesion changed little inthe experimental scope, but the initiative adhesion and 180 peel strength were improvedapparently.The pressure-sensitive adhesive emulsion with solid content of 50% could also be preparedthrough the mini-emulsion polymerization of glyceride of disproportionated rosin (DRG) withacrylates. Because there were a lot of hydroxyl and carboxyl groups on the molecules of DRG,the chain transition made the polymer's molecular weight decline sharply, and resulted in thesharp decrease of durative adhesion of polymers. If a part of AR-2-HEA (3.75 %) was added,the polymer emulsion's durative and initiative adhesions and 180°peel strength were allimproved through the proper crosslinking. The experimental results indicated that, the composite emulsion of rosin derivatives and acrylate was a kind of pressure sensitive adhesivewith excellent properties.The polymer's glass transition temperature was dropped down through thecopolymerization of AR-2-HEA with MMA/BuA (50/50, 60/40), and the yield strength ofpolymer film was also weakened, but their elongation rate at break and tensile strength wereimproved. The polymer's heat resistance was improved through the introduction of AR-2-HEA.The polymer's glass transition temperature was dropped down through the copolymerization ofDPR-2-HEA with MMA/BuA (50/50), and the yield strength of polymer film was alsoweakened, but their elongation rate at break and tensile strength were improved.5. Primary investigation on the hollow particle of turpentine and polystyreneThe polymer microsphere with hollow or solid-liquid core-shell structures has wideapplication prospect. In this paper, the turpentine was used as the stabilization agent to preparethe turpentine/styrene emulsion with liquid bead size of 1～2μm. The styrene polymerizationwas initiated by oil-soluble initiators like AIBN and BPO, and the resulted particle size anddistribution was consistent with the monomer beads. During the polymerization the turpentineand polystyrene experienced a phase separation in the particle due to the insolubility ofpolystyrene in turpentine. Finally the formed polymer particle had a microstructure withpolystyrene as the shell and turpentine as the core. Such a structure had been confirmed byTEM and GC-MS.