The development trend and research progress of saturated polyester resins for thermosetting powder coatings

Abstract:
reviews the research status of polyester resins for thermoo-solid powder coatings, summarizes the development trend of polyester resins for powder coatings, and puts forward the problems to be solved in the industry.0
introduction
powder coating as a widely used environmental protection coating, in China's rapid development, of which thermoo-solid powder coating varieties accounted for the vast majority. Over
past
years, the average annual growth rate has reached more than
9%
, which is the largest growth rate in one of the

.
2012
China's powder coating production reached
1.045 million

t
, ranking first in the world. The rapid development of powder coatings has also led to the rapid growth of upstream raw material polyester resins, with
the production of polyester resins for powder coatings reaching
382,000
t
in

2012, with an average annual growth rate of
8.
5% in
5
. As competition in the industry intensifies, the application of powder coatings has expanded, and various functional powder coatings have been put on the market. In addition, in recent years, with the increase of energy conservation and environmental protection efforts, manufacturers of energy conservation and consumption reduction demand gradually increased. Driven by this background, many new low-temperature curing type, thermal transfer type, ultra-weather-resistant powder coating polyester resin and other products continue to be
introduced
1.
. The development trend of polyester resins for powder coatings
1.1
Environmentalization
In recent years, the toxicity of
TGIC
has been affected, as well as the enhancement of environmental awareness, and the demand for polyester resins using non-toxic environmentally friendly
HAA
-type curing systems has been increasing. According to

,


HAA
polyester increased by

12.1%
in 2012 compared to 2012
, while the
TGIC
solidified type increased by only about
2%
, and it can be clearly felt that the environmental protection of polyester is becoming more and more important. Because the reaction activity of
HAA
system is high, and when curing will release by-product water, which can easily cause the phenomenon of thick membrane pinholes, on the other hand, because of the high reaction activity, faster curing speed, the smooth performance of the system is also poor, and moreover, because of the
HAA
system of poor yellowing performance, curing and baking is prone to yellow change. Domestic mainly focused on solving
or circumventing
shortcomings of haA to study
alternative
TGIC varieties. When synthesizing polyester resins for
β-
hydroxyacetamide-cured weather-resistant powder coatings, the
g
, viscosity and reaction activity of the resin are controlled mainly by designing different reactant monomers, and the viscosity of the system is reduced by the selection of the resin polyester
monomer structure to obtain the resins
the trend of environmentalization is the study of polyester resins that do not contain organo tin. Polyester resin synthesis of powder coatings with organic tin compounds as catalysts, because of the catalyst catalytic efficiency, uniform synthesis reaction, synthetic resin color good, in the domestic polyester plant has been widely used. In recent years, by Europe and the United States and other developed countries market influence, there have been many countries issued relevant regulations or standards to limit the use of organo tin.VX
II
to the EU'
and
regulations.
compounds of concern in the
include
TBT
, tribenzene tin compounds and butyltin (
DBT
), and
DOT
) compounds, the first two of which are officially limited to
2010 July
,
2017
1
, and the 2nd is limited to 11
2012On the 19th, IKEA and other downstream manufacturers proposed that the content of coated organo tin needs to be controlled below
1.0×10-6
, Pan from art and other

. Polyester used in the synthesis of powder coatings for non-butyl tin catalysts was studied to obtain a resin equivalent to the performance of catalysts that routinely use organotin.1.2
Energy Saving With the increasing demand for energy conservation and emission reduction, more and more enterprises and institutions began to attach importance to the research and development and application of energy saving and emission reduction technology, mainly in the field of powder for low-temperature curing type and rapid curing powder coating application and promotion, for the current low-temperature cured powder coating, mainly depends on the research and development of low-temperature cured polyester resin. At present, the curing conditions of traditional powder coatings are generally
180 to 200
degrees C
/10 to 20 min
, the general baking temperature is reduced by
10
degrees C
, energy savings of about
10%
. For low temperature curing, the hybrid type (epoxy curing type) is a more mature variety, can reach
160
degrees C
/10 to 15 min
curing level, the outer orange peel is heavier, mainly through the addition of curing promoter obtained;
Primid
system mainly has acid value of
30mg KOH/g
about
95/5

type for
160
degrees C
/15 min
and
160
degrees C
/10 Min
mostly used acid value of
50 mgKOH/g
about
93/7
type, by increasing the acid value, to obtain a higher reaction activity;
more
varieties in the TGIC system can meet
160
degrees C
/15 min.
curing, mainly through flexible monogam selection and curing promoter combination, suitable for low-temperature curing curing promoter mainly has
4
categories: the alkalis represented by shamide, the hum salts represented by halide , the metal chelate represented by acetyl acetone cobalt and the cation compounds represented by boron tropluoride.In present, Li Yong and otherby introducing different reaction activity and smooth monomers such as hexicillic acid, methyl propylene glycol, cyclohexane methamphetamine, etc., to reduce the viscosity of the system, change the molecular structure of polyester resin, synthetic suitable for
β-
The alkylamide curing agent
160
degrees C
/15 min
the end-of-term pyride polyester resin used for curing, the basic performance of conventional resins
180
degrees C
/15 min
equivalent.
the acid value of

90
to 110 mgKOH/g
, melting viscosity of
5 to 15 Pa.s
(
130
C
),
Tg
is
Hybrid polyester resins from 42 to 52
degrees C
can be cured by adding
RB31
curing promoter (in
2%
dosage) containing a ring structure to meet the requirements of
130
degrees C
/25 min
.
Wang Guozhi, etc.

through the use of antibutyl diacid, shunbutene diacid and other monosomes of low-temperature reaction activity, in a smooth good monogasic heic acid, diacid acid and curing With the cooperation of the promoter, the acid values of
30 to 40 mg KOH/g
,
Tg


55 to 62
Polyester resin
coatings for outdoor powder coatings at
140
degrees C
/30 min
,
150
degrees C
TGIC
system
20 min
160

/15min
160
C.aspect of energy conservation is rapid curing. It is concentrated in obtaining high turnover efficiency by reducing curing reaction time, thus achieving energy saving effect. The curing temperature of powder spraying plants is generally prone to fluctuations, often low, in order to better obtain a stable degree of curing, many manufacturers often add curing promoter on the basis of conventional curing temperature products, or directly choose low-temperature curing or fast curing products.1.3
Functional With the increasingly fierce competition for powder coatings, the general industry profits are getting lower and lower, in order to obtain better profit returns, more and more enterprises began to turn to higher value-added market segments; In general, more and more polyester resin research and development tend to functional development. Specifically reflected in the ultra-weather-resistant powder coating polyester series
11
(
)
large curtain wall, ceiling, solar water heater), high temperature powder coating polyester, thermal transfer powder coating polyester, high decorative powder coating polyester
, high
toughness (roll)
/
Polyester for impact-resistant powder coatings, polyester for thin powder coatings, polyester for water-resistant powder coatings, polyester modified technology research (silicone, acrylic, fluorine monomer, etc.), polyester for one extrusion of anti-light powder coatings, overspending polyester, semi-crystalline
polyester
among them, the synthesis of polyester for high temperature-resistant powder coatings mainly takes the method of improving relative molecular mass, increasing cross-link density and adding antioxidants to improve its temperature resistance level, when using ordinary pigments such as niobium sulfate and titanium dioxide, it can generally reach
300
At the level of
degrees C, a higher temperature resistance level can be obtained if polyester uses silicone modified and talc powder, hollow powder, quartz powder, and mica powder as fillers to prepare powder
coatings
Overspending polyester
(18-19)
is generally a multi-hydroxymethyl propane (
DTMP
), tetryptonol and other multi-official groups as nuclear monomers, with dihydroxymethyl acid (
DMPA

AB
type monosome as a branch-like growth chain synthesis, because the overspending molecules are spherical, and the end of the base is mostly a hydroxyl or hydroxyl class of the official energy group, melting viscosity is also low, so it has a high reaction activity, in low temperature curing and high level powder coating has a greater prospect. Semi-crystalline resin is also one of the hot spots in recent years, characterized by high
Tg
, low melting viscosity, excellent leveling properties after curing, and high potential value in solving powder leveling.in the study of polyester-modified powder coatings, Fan Hong and other
,20?
added a small amount of silicone active resin
Z-6018
, obtained silicone modified polyester, modified resin
Tg
, melting viscosity slightly decreased, after curing coating film weather resistance improved, when the amount added is
1%
, the overall performance is better. In the area of fluorine-containing modified polyester, Jinyunquan reacts by mixing alkyl binary alcohols, cyclic acids, fluorine-free monocyclic oxygen-based compounds and fluorine-containing monocyclic oxygen-based compounds, and the reaction product is diluted with acetone. Added to the distilled water, precipitation precipitated to obtain fluorine polyester resin, prepared into a powder coating, the hardness of the coating film, boiling water, acid and alkalinity have been improved, and the adhesion to the substrate has not been reduced.1.4
Low cost
powder coating competition has also led to the upstream polyester resin began to develop low-cost polyester resin, mainly reflected in the use of lower-cost monomer to reduce the formulation costs of the resin, but due to the limitations of powder processing methods and the development of synthetic technology, the cost reduction in the use of conventional monomer is also relatively limited. In addition, there are researchers using waste
PET
polyester by melosome synthesis of mixed polyester, but there is a deep color, product performance is not equal, poor transparency, high
crystallization disadvantages