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CN-122012002-A - Polyurethane pouring sealant with thermal trigger dual defoaming mechanism and preparation method and application thereof

CN122012002ACN 122012002 ACN122012002 ACN 122012002ACN-122012002-A

Abstract

The invention discloses a polyurethane pouring sealant with a thermal trigger dual defoaming mechanism, and a preparation method and application thereof. The pouring sealant composition comprises a polyurethane prepolymer, a curing agent and a heat-triggered core-shell structure defoaming microsphere, wherein the defoaming microsphere sequentially comprises an inner core containing defoaming active substances, a heat-softening polyurethane microgel middle layer formed by partially crosslinking reaction of polycaprolactone polyol and polyether polyol, and an organosilicon-polyurethane hybrid copolymer shell, wherein the softening initial temperature of the heat-softening polyurethane microgel middle layer is 45-60 ℃, and the polymer chain of the organosilicon-polyurethane hybrid copolymer shell contains active groups capable of reacting with isocyanate groups. According to the invention, the delayed release of the solidification heat release period is realized through the heat softening of the intermediate layer, the defoaming component of the inner core is delivered to the micro-bubble area, the shell fragments are chemically bonded with the matrix, the bubble content of the pouring sealant after solidification is obviously reduced, the dielectric strength is improved, and the adhesive has excellent storage stability, so that the adhesive is suitable for packaging protection of electronic devices needing to be heated and solidified.

Inventors

  • ZHU ZHOUSHAN

Assignees

  • 迪瓦化学(广东)有限公司

Dates

Publication Date
20260512
Application Date
20260324

Claims (8)

  1. 1. The polyurethane pouring sealant composition is characterized by comprising a polyurethane prepolymer, a curing agent and a heat-triggered core-shell structure defoaming microsphere, wherein the heat-triggered core-shell structure defoaming microsphere is of a three-layer core-shell structure and sequentially comprises the following components from inside to outside: An inner core comprising a carrier silicone oil and a defoaming active of hydrophobic silica; An intermediate layer which is a thermosoftening polyurethane microgel formed by partial crosslinking reaction of a polycaprolactone polyol and a polyether polyol, said microgel having a softening initiation temperature of 45 to 60 ℃ as determined by differential scanning calorimetry, and The shell is an organosilicon-polyurethane hybrid copolymer, and the polymer chain of the shell comprises active groups capable of reacting with isocyanate groups.
  2. 2. The polyurethane potting adhesive composition according to claim 1, wherein the weight mixing ratio of the polycaprolactone polyol to the polyether polyol is 1 (0.25-4), the number average molecular weight of the polycaprolactone polyol and the polyether polyol is 300-500 independently, and the functionality is not less than 3.
  3. 3. The polyurethane potting adhesive composition of claim 1, wherein the glass transition temperature of the shell is more than or equal to 70 ℃ and the thickness is 200-600nm.
  4. 4. The polyurethane pouring sealant composition according to claim 1, wherein the carrier silicone oil is at least one of dimethyl silicone oil, methyl phenyl silicone oil or fluorine modified polysiloxane in the inner core, and the specific surface area of the hydrophobic silica is 150-300 m 2 /g.
  5. 5. The polyurethane potting adhesive composition of any one of claims 1 to 4, wherein the average particle diameter D50 of the heat-triggered core-shell defoaming microspheres is 10-40 μm.
  6. 6. The polyurethane pouring sealant composition according to claim 5, wherein the addition amount of the heat-triggered core-shell structure defoaming microspheres is 0.1-1.0 wt% of the total weight of the pouring sealant composition.
  7. 7. A method for preparing the polyurethane pouring sealant composition according to any one of claims 1 to 6, which is characterized in that the heat-triggered core-shell defoaming microsphere and the curing agent component are mixed and dispersed uniformly and then mixed with the polyurethane prepolymer.
  8. 8. Use of the polyurethane potting adhesive composition of any one of claims 1 to 6 in packaging of electronic devices requiring heat curing.

Description

Polyurethane pouring sealant with thermal trigger dual defoaming mechanism and preparation method and application thereof Technical Field The invention belongs to the technical field of pouring sealants, and particularly relates to a polyurethane pouring sealant with a thermal trigger dual defoaming mechanism, and a preparation method and application thereof. Background Polyurethane pouring sealant is widely applied to encapsulation protection of electronic devices due to excellent electrical insulation, adhesion and ageing resistance. However, in the whole process from mixing, filling and curing, the problems of bubble generation and residue always exist, namely millimeter-sized bubbles mechanically involved are blocked by high viscosity and are difficult to escape in the stirring and mixing period, dynamic-migration bubbles are easy to form macroscopic defects at structural dead angles in the filling and leveling period, and dissolved air is separated out in the most critical reaction curing period due to heat release of a system, and meanwhile, isocyanate reacts with trace moisture to generate carbon dioxide, so that a large number of micron-sized bubbles are formed. Such bubbles are immobilized in the gel network, cannot be eliminated by migration or floating, and can significantly degrade the dielectric, thermal and mechanical properties of the material. The prior defoaming technical means has limitations and can only partially solve the problems. The physical defoaming method is ineffective to microbubbles in the curing period, the direct addition of the chemical defoaming agent can not achieve the two difficult problems that the action stage is single, the early-stage large bubbles and the later-stage microbubbles cannot be taken into account, and interface defects are easily caused by excessive addition, and part of defoaming materials with core-shell structures can realize trigger release, but often rely on uncontrollable modes such as mechanical shearing and the like, or use physical phase change materials to introduce residual risks, cannot be matched with the thermal field change in the polyurethane curing process accurately, and can not ensure that a substrate has no microdefect residues after defoaming. Therefore, developing a defoaming system that can intelligently respond to a process, precisely act on a curing stage, and can be chemically integrated with a substrate to avoid introducing new defects is a technical problem to be solved in the art. Disclosure of Invention In order to solve the problem that the prior art cannot achieve the full flow bubble control of polyurethane encapsulation and particularly eliminate the debilitation of micro bubbles in the curing period, the invention provides a polyurethane pouring sealant composition with a heat-triggered dual defoaming mechanism, which comprises heat-triggered core-shell structure defoaming microspheres, wherein ① is used for providing physical defoaming and protecting a core by a high Tg rigid shell in the early stage of the process, ② is used for realizing accurate heat triggering with curing heat release by an intermediate layer with a specific softening temperature, and ③ is used for ensuring that a substrate has no new defect after defoaming by a core and shell material capable of being integrated in a reaction mode. In order to achieve the above purpose, the present invention provides the following technical solutions: The polyurethane pouring sealant composition with the heat-triggered dual defoaming mechanism comprises a polyurethane prepolymer, a curing agent and heat-triggered core-shell structure defoaming microspheres, wherein the heat-triggered core-shell structure defoaming microspheres are of a three-layer core-shell structure and sequentially comprise the following components from inside to outside: An inner core comprising a carrier silicone oil and a defoaming active of hydrophobic silica; An intermediate layer which is a thermosoftening polyurethane microgel formed by partial crosslinking reaction of a polycaprolactone polyol and a polyether polyol, said microgel having a softening initiation temperature of 45 to 60 ℃ as determined by differential scanning calorimetry, and The shell is an organosilicon-polyurethane hybrid copolymer, and the polymer chain of the shell comprises active groups capable of reacting with isocyanate groups. Wherein the polyurethane prepolymer is used as a main resin component of colloid, and is usually polyether or polyester prepolymer terminated by isocyanate groups (-NCO), and the curing agent comprises components reacted with the polyurethane prepolymer, such as polyamine or polyalcohol curing agent, chain extender (such as 1, 4-butanediol), catalyst (such as organic tin compounds), filler (such as aluminum hydroxide and silicon micropowder) and the like. The heat-triggered core-shell structure defoaming microsphere is a core functional additive, and the adding amount of the heat-triggered