How Disposable Diapers Keep Skin Dry Using Porous Plastic Sheets
A 1970 patent by Procter and Gamble describing a specialized plastic top layer for diapers that allows liquid to pass through while keeping the baby's skin feeling dry.
Original patent title: “Topsheet for disposable diapers”
A 1970 patent by Procter and Gamble describing a specialized plastic top layer for diapers that allows liquid to pass through while keeping the baby's skin feeling dry. Granted to Procter and Gamble Co in 1970 with 133 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This patent describes a hydrophobic, porous plastic film used as the inner layer of a disposable diaper. The material is designed with specific hole patterns that allow urine to quickly pass through into an absorbent core. Because the material is hydrophobic, or water-repelling, it prevents the liquid from flowing back to the surface, effectively separating the moisture from the baby's skin. This mechanism was a fundamental shift from using cloth or non-porous materials that would trap wetness against the skin.
The gap
What does this patent NOT cover?
- Does not cover the absorbent core material itself, only the top layer in contact with the skin.
- Does not cover non-plastic or fabric-based top layers that rely on absorption rather than fluid transport through holes.
- Does not cover diapers that do not use a hydrophobic material to prevent liquid back-flow.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The innovation lies in using a hydrophobic material with specifically sized apertures that exploit surface tension to let liquid move in one direction only, effectively creating a one-way valve for moisture.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Pampers disposable diapers
Generic disposable diaper top sheets
Why it matters
The bigger picture
This invention was a cornerstone in the development of the modern disposable diaper industry. By solving the problem of 'wet-back'—where moisture returns to the skin surface—it enabled the mass-market success of brands like Pampers. It transformed diapers from a simple absorbent pad into a sophisticated engineered product.
Filed
December 20, 1966
Granted
January 13, 1970
Market context
Who's building on this
Companies in this space
Procter and Gamble continues to iterate on this technology, focusing on advanced non-woven materials and micro-apertures. Other major players like Kimberly-Clark have also built extensive patent portfolios around similar fluid-management layers in their Huggies product lines.
Market impact
This patent helped establish the disposable diaper as a reliable, high-performance consumer good. It triggered decades of R&D in material science to improve comfort and leak protection, effectively making cloth diapers a niche alternative in many developed markets.
Claim 1 — Plain English
What this patent covers
This patent describes a hydrophobic, porous plastic film used as the inner layer of a disposable diaper. The material is designed with specific hole patterns that allow urine to quickly pass through into an absorbent core. Because the material is hydrophobic, or water-repelling, it prevents the liquid from flowing back to the surface, effectively separating the moisture from the baby's skin. This mechanism was a fundamental shift from using cloth or non-porous materials that would trap wetness against the skin.
The clever bit
The innovation lies in using a hydrophobic material with specifically sized apertures that exploit surface tension to let liquid move in one direction only, effectively creating a one-way valve for moisture.
What it does not cover
- Does not cover the absorbent core material itself, only the top layer in contact with the skin.
- Does not cover non-plastic or fabric-based top layers that rely on absorption rather than fluid transport through holes.
- Does not cover diapers that do not use a hydrophobic material to prevent liquid back-flow.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$66K – $211K
Midpoint $132K · expired or expiring · industry ×2.2
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
Duncan, R. C., & Gellert, D. A. (1970). How Disposable Diapers Keep Skin Dry Using Porous Plastic Sheets (U.S. Patent No. 3,489,148). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3489148/disposable-diaper-topsheet
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Disposable Diapers Keep Skin Dry Using Porous Plastic Sheets cover?
A 1970 patent by Procter and Gamble describing a specialized plastic top layer for diapers that allows liquid to pass through while keeping the baby's skin feeling dry.
Who owns patent US 3489148?
Procter and Gamble Co owns this patent, granted in 1970.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 3489148 cited by?
This patent has been cited by 133 later patents that build on its ideas.
What problem does this patent solve?
This invention was a cornerstone in the development of the modern disposable diaper industry. By solving the problem of 'wet-back'—where moisture returns to the skin surface—it enabled the mass-market success of brands like Pampers. It transformed diapers from a simple absorbent pad into a sophisticated engineered product.
What does this patent NOT cover?
Does not cover the absorbent core material itself, only the top layer in contact with the skin.
Same assignee
More from Procter and Gamble Co
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